My books are generally available at your local bookseller. If one's not in stock, they'll be happy to place an order for you. Here's a quick list of sources for my titles. Oh, and they carry other books as well. Buy them; you really need to read more.
And, of course, remember your local LGBT bookseller. I wish that went without saying, but it doesn't.
(The following is a work in progress. Did I miss you in this listing? Let me know.)
(Ann Arbor, MI)
InsightOut Book Club
Barnes & Noble