From Slate:

No. One cannot just go around reading the books of friends and acquaintances. The exceptions to this rule are few and obvious—looking at a draft to give constructive criticism, searching for thinly veiled gossip, so on. The sound reasons for obeying the rule are many and various. Like, what if the book turns out to be a best-seller? If you read the future best-seller and determine it to be bad, then you have to resent your friend’s success. If you read it and determine it to be good, then you have to envy his talent. There’s no way to win. Never read your friends’ books, probably. Instead, buy a copy, read the first and last sentences, skim the fourth chapter, cast a forensic eye at the acknowledgments page, and give it as a gift to someone else.

I see things a bit differently. I generally would not read a friend’s book draft to give criticism, constructive or otherwise. I already get a steady supply of unpublished work in the form of MMIP submissions, and between that and my own work I don’t have time to delve into other people’s writing problems. Also, I don’t generally bother myself about whether a book becomes a bestseller, and I’m not keen on professional envy. I understand that this is show business, and the amount of money and attention a author’s book receives comes from a mysterious mix of talent, commercial appeal, hustle, and timing. Envy’s a wasted emotion.

In the end, if I felt inclined, I’d probably buy a friend’s book without mentioning it. If I read it and liked it, I’d say something. If I disliked it, my friend need never know I picked it up. That’s the nice thing about books. Reading is a private act. Try going to a friend’s movie premiere and then having to screw on a smile and talk to them after two of the worst hours you ever spent outside a dentist’s office. You end of saying things like. “You must be so…I mean, thrillers. I like thrillers and movies and this was definitely one of those two…things…well, we should be going, you know. Traffic. That was…Bye.”

Of course, none of my friends have ever disliked my work. Right? RIGHT?!?