From what I've read of Theodore Sturgeon's work before, Robert Heinlein and Stephen Donaldson seemed unlikely choices for, respectively, the foreword and afterword. On dipping into the novel, however, it began to make sense. Sturgeon's Godbody is in some ways an amalgam of Heinlein's own two Smiths - Woodrow Wilson and Valentine Michael, and the focus on a 'free love makes everything better' theme fits nicely with Heinlein's late period wish fulfillment stories. Donaldson's is a more intellectual and reasoned commentary, but also more interesting.
I agree with Donaldson that Sturgeon's premise is weak. Essentially, the title character, Godbody, helps people realize their true selves by freeing them from sexual repression. That's not a spoiler - it happens to the first character, in the first chapter. Sturgeon writes unselfconsciously about sex, and he approaches it from a variety of angles. It's reasonably well done, but not particularly interesting. What works better is the character studies that form the basis of the book's individual chapters. It's the fact that these characters grow that's interesting here, not how they do it.
Godbody himself is a mild cypher that comes clear without much surprise at the end. The most interesting thing about him is the very down-to-earth tone that Sturgeon has given this mystical central figure.
While the book has a strong defining theme, it lacks a clear plot, and the chapters follow each other in something of a jumble. The middle of the book slows considerably, in part because Sturgeon is so busy describing each character's attitudes toward sex that he forgets to move the story forward. The book does improve thereafter, with a satisfying, if simplistic ending.
Unlike the characters in the story, your life won't be changed by meeting Godbody, but you might spend a pleasant afternoon with him and his friends.