Some books pre-1978 MAY contain lead, IF they have hand tinted tipped-in illustrations. Lead was still used in artist grade paints. Now, those types of illustrations are A) rare B) Expensive C)generally not intended for children D) old. There aren't a lot of those around.
The tiny amount of lead used in those is so low as to be of no concern. If you can even FIND them in some kind of affordable price range to be used in crafts. If the book is intact, expect to spend BIG BUCKS. Your kid is getting way more exposure to lead through your drinking water or exposure to dirt. (yes, dirt)
The only case of lead contamination related to modern kids books actually doesn't involve the BOOK. If you've ever seen those "Magic X" books that come with a necklace, one of those was recalled due to lead content in the necklace. No problem with the book, just the necklace stuck to it.
I am all for having the trinkets and doodads that are stuck to books as extras (necklaces, googly eyes, foil shinies, sound bars, etc) tested for lead and pthlates. Those actually have a chance of containing those AND if detached can be a chocking hazard. Since those interactive books are largely aimed at wee little ones, it also makes sense that they may well end up in little mouths.
Unstuffed cloth books should skate by the regulation, those plastic tub books should be tested for pthalates.
I know some people are said to have an appetite for books, but a standard paper book itself should not hurt you. Fiber is good for you!