the book of life vs. the books of works
From Dave Coverley's Speed Bump...
This is a reference to Rev 20:12's "book of life"-- those who will be judged in light of Christ's atoning sacrifice on their behalf. In contrast, there are the (many/plural) "books of the works" of those who will be judged by their works.
The book of life can be singular because there are relatively few people going to heaven or because the entries are much smaller. To note, the book of life only requires a mention of my name.
The books of works must have more volume, given the extent of even one individual's good and bad works. Unfortunately, for those choosing this route, the Bible explains that one much be perfect.
Don't try to earn God's salvation; it can't be done. Accept the grace of God, offered to you freely.