There are numerous problems with Christian Science, with the most serious being the fact that it isn't Christian, practitioners employ mind-control techniques (which is why they've been accused of being a cult) and it promotes the dangerous idea that people should shun all conventional medicine in favor of spiritual healing - a credo that has caused the deaths of too many people whose lives should not have been wasted.

Let's start with a little history.

Christian Science was founded by a devout Christian woman named Mary Baker Eddy (1821-1910) who suffered from a variety of ills and dabbled in various alternative treatments rather than subject herself to the medical treatments available during the 19th Century. In 1862, she sought help from a healer named Phineas Parkhurst Quimby of Maine. Quimby's healing methods incorporated Anton Mesmer’s ideas of animal magnetism and involved laying hands on a sick patient's head and abdomen to encourage an alleged magnetic healing force to flow through them. It was essentially a combination of mental suggestion and what we would now call therapeutic touch. He used the method to both diagnose and heal maladies of all sorts. As far as Quimby was concerned, all conventional medicine was useless and that disease itself was an "error." Only health was "truth."

Eddy was intrigued, and believed her health improved substantially under his care but, as is often the case with placebo healings, her ills soon returned and she went back  to Quimby. By this point, she had managed to convince herself that only he could help her because he had discovered Jesus' healing method.

The turning point came in 1866 when she suffered a severe fall on an icy sidewalk that caused a serious spinal injury. Because Quimby had died a month earlier, she could no longer turn to him for help. Instead, she searched out all of the stories of Jesus' healings in the Bible and suddenly found herself healed. She would eventually refer to this event as the moment she discovered Christian Science.

She began to develop a theory based on a combination of Quimby's techniques and the Bible, and published the book, Science and Health, in 1876. She claimed God was the author of the book and she was only the writer. The decision was made to name her philosophy Christian Science upon which she founded the church, which is known officially as The Church of Christ, Scientist, in 1879.

Perhaps the most distinctive - and controversial - teaching of Eddy's church is that creation is entirely spiritual and perfect and that matter does not exist. Sin, sickness and death also do not exist - we just think they do. "The only reality of sin, sickness, or death is the awful fact that unrealities seem real to human, erring belief, until God strips off their disguise" (Science and Health, 472:27-29).

Mary Baker Eddy's burial memorial

This is why most members refuse medical help for disease, although the decision to seek physical treatments is left up to the individual. Devout members refuse medications and all medical aid, oppose vaccination and quarantine for contagious diseases (although they advise members to obey state laws), allow a physician or midwife during childbirth and will only allow a physician to set a broken bone if no medication is administered.

Adherents believe illness is nothing more than an illusion caused by a faulty belief system and employ prayer in order to replace bad thoughts with good ones. In other words, they "treat" patients by employing mind-control tactics to convince them that sickness is not real. These "consultations" can take place in person, by telephone, or even by mail.

The core teachings of Christian Science can be found in the "Scientific Statement of Being," which is read at every church service:

There is no life, truth, intelligence, nor substance in matter. All is infinite Mind and its infinite manifestation, for God is All-in-all. Spirit is immortal Truth; matter is mortal error. Spirit is the real and eternal; matter is the unreal and temporal. Spirit is God, and man is His image and likeness. Therefore man is not material; he is spiritual. (Science &Health, 468)

That this group operates in a cult-like fashion has been revealed by former members such as Linda Kramer who wrote a book entitled  Perfect Peril: Christian Science and Mind Control which details the mind-control and cult-like qualities of this "religion."

“It’s ‘mystical manipulation,’” Kramer told the Christian Post (CP).  "For instance, when conditions such as colds or menstrual cramps get better with time, the Scientists believe it's the prayer that works. . . . Any cult leader is going to twist things to make them seem supernatural,” Kramer said.

She also said that Eddy was very concerned about "mental malpractice," which is the belief that someone's negative thoughts can cause illness upon another. Apparently, Eddy believed her third husband Asa was mentally murdered with arsenic that was mentally administered, Kramer reported.

By playing fast and loose with Scripture, taking verses out of context or assigning new "spirtualized" meanings to them, Eddy tries to convince adherents that her religion is following Christ. It is - but it's not the Christ you and I are following.

Christian Science Mother Church in Boston

For instance, Christian Scientists teach that Jesus is divine, but not God, and that His human nature is a separate entity from the divine Christ. Eddy writes: "Jesus Christ is not God, as Jesus himself declared, but is the Son of God" (Science and Health, 361:12-13). This is in direct contradiction to Scripture. In John 1:1, we read: "In the beginning was the Word, and the Word was with God, and the Word was God." St. Paul also tells us in the Letter to the Colossians: "For in Him all the fullness of Deity dwells in bodily form" (Col. 2-9).

Eddy also rejected the doctrine of the Trinity, calling it polytheistic (Science and Health, 256:9-11). Her idea of the threefold nature of God was to define it as a trinity of "God the Father-Mother, Christ the spiritual idea of sonship, and divine Science or the Holy Comforter" (Science and Health 331:26-332:3). Eddy reveals her lack of understanding about basic Christian truths when she calls the Trinity "polytheistic" which means multiple gods. Christians don't believe the Trinity consists of multiple gods. The Trinity is three Persons in one God. There are many Biblical verses that demonstrate the Trinitarian aspect of God, such as, "Go therefore and make disciples of all the nations, baptizing them in the name of the Father and of the Son and of the Holy Spirit . . . (Matt 28:19).

In denying the existence of all matter, including man's physical body, Christian Scientists then deduce that man is "incapable of sin, sickness, and death." These are due to the "effects of error", not sin. In the question and answer section of Eddy's Miscellaneous Writings, she's asked, "If there is no sin, why did Jesus come to save sinners?" Eddy answers: "Jesus came to seek and to save such as believe in the reality of the unreal; to save them from this false belief; that they might lay hold of eternal Life ..." (p. 63).

Needless to say, there is nothing Christian about Christian Science, but what is equally troubling are the many horrific case histories of people who were subjected to unspeakable suffering and death because of members' refusal to seek medical attention.

In fact, so many children suffered needless deaths at the hands of Christian Scientists and other cults that eschew medicine that an organization has been started to work for legal reforms to protect them from these abuses. It was started by Rita Swan, Ph.D., whose 16 month-old son Matthew died of meningitis in 1977 while under the care of two Christian Science practitioners. She launched Children's Healthcare is a Legal Duty, Inc. (CHILD).

During one lawsuit waged by CHILD against the Christian Scientists, testimony revealed that the church gives no training to practitioners on how to evaluate the seriousness of a person's condition. A news released by CHILD in the wake of another suit involving Christian Science nurses in 1996 reveals just how ill-prepared these "nurses" are for healing.

"Christian Science nurses cannot take a pulse, use a fever thermometer, give an enema or even a backrub. They have no training in recognizing contagious diseases. They have been retained to attend sick children and have sat taking notes as the children suffered and died, but have not called for medical care nor recommended that parents obtain it. The notes of these . . . nurses indicate that they observed children having 'heavy convulsions,' vomiting repeatedly, and urinating uncontrollably. They have seen the children moaning in pain and too weak to get out of bed. They have seen their eyes roll upward and fix in a glassy stare. One Christian Science nurse force-fed a toddler as he was dying of a bowel obstruction."

Thankfully, membership in the church has been declining rapidly in the last four decades. Between 1971 and 2009 the number of U.S. practitioners and teachers listed in the Christian Science Journal fell from about 5,000 to about 1,160 and the number of churches fell from about 1,800 to about 900. Its membership is said to have dropped from 268,915 members in 1936 to little more than 30,000 today.

I'm not sure if this answer fits the "concise" criteria you requested (forgive me!) but this "religion" needs to be exposed for what it is - a dangerous cult.