Tolstoy lists the Gospels as having had an "enormous" impact on him during two key periods, his youth (from age 14 to 20) and the period from age 50 to age 63, his age when he drew up his list of influences. It is safe to say that the Gospels remained enormously important to him for the remainder of his life. In his Confession, Tolstoy describes how his childhood faith in the Russian Orthodox Church declined during his youth, how he led a dissolute life as a young man, how he diverted himself "from any search for the meaning of life" for the first 15 years or so after his marriage. Then things changed. Tolstoy would increasingly experience bouts of despair and bewilderment when "Why [live]?" became a question that he needed to answer. Tolstoy found that he literally could not go on living unless he found answers to questions about the meaning of life.
At this point, Tolstoy returned to the Gospels, which he studied in their original Greek. The Gospels contained Jesus' teaching in what Tolstoy considered to be its purest form. Tolstoy was quick to point out that the Russian Orthodox Church, along with other churches, had incorporated as doctrine many beliefs and had developed many rituals that distorted and detracted from Jesus' teaching. Tolstoy wanted to go back to basics.
The Gospel in Brief is Tolstoy's version of the Gospels. Tolstoy integrated the canonical accounts of Matthew, Mark, Luke and John into one unified version of Jesus' life and teaching. As he did this, Tolstoy also left out the material from the Gospels that he felt was extraneous, such as the accounts of his miracles and of Jesus' resurrection. (Tolstoy was aware that Thomas Jefferson had undertaken a similar "revision" of the Gospels.) For Tolstoy, Jesus' teaching was a "light" that gave life meaning, and the rest didn't matter or even got in the way.