The City and the Pillar by Gore Vidal (1948).
Vidal's third novel is infamous for being one of the first mainstream novels to portray a sympathetic gay man who was a regular "All-American" guy. Jim Willard and Bob Ford are one year apart in high school, both athletes, and best friends. Bob goes with a lot of girls, but Jim is more attracted to Bob. One night after Bob's graduation, and just before he goes off to join the Merchant Marine, Jim and Bob go camping at an isolated cabin and after a day of skinny dipping and a night of wrestling by the fire, the two of them have sex. Bob leaves, promising that he will write and that Jim will join him at sea after he graduates the next year, but after a couple of letters the notes from sea dry up.
Jim graduates and disappoints his parents by ditching his college plans and heading to New York to join the Merchant Marine and find Bob. He doesn't find his friend, but he does find a position on a ship, which he later abandons for California. He has a lot of casual sex and a few more serious relationships (one with a famous actor, and one with a semi-famous writer), but in the back of his mind he is always waiting for Bob. When, at the end of the book, he finally gets to spend another night alone with his best friend, things do not turn out the way he planned.
I liked this book. The straightforward prose is misleadingly simple, and hides a interesting structure and some good character development. Although Jim is our protagonist, we never get a really good sense of him as a character, and I think that is deliberate. Instead, the side characters are filled with details and dimensions that end up teaching us about Jim.
Vidal revised this novel in the mid-1960s and his biggest change was altering the climactic last chapter. It is still dark and dramatic, but different. I'll be interested to talk that out with my fellow DAFFODILS...
[You can read a bit about the reception of the book and Vidal's views on writing it here.]