I noticed going through some printed books that almost all of them have an excerpt of the book or book reviews (or both) on the very first page as soon as you open it up. I understand the reason for doing this (a means of marketing so people can conveniently get a quick peek at the book's contents as soon as they open it up instead of thumbing through the thing), but I'm wondering if there's any sort of rule for doing this? Is there a word limit for putting excerpts on the first page? What's the ideal word limit if there is one? Are there any other things to consider?