by是根据的意思，book是书本的意思。by the book这个习惯用语的意思是“循规蹈矩，照章办事”。

If you are looking for someone to do some creative accounting - you know, think up ways to avoid paying what you are supposed to - then I'm not the guy. I do everything by the book. Sorry.

如果你要找人做帐，想办法帮你逃税，那你找错人了。我从来都是照章办事。对不起。