As promised, I'm going to give you a list of my favorite books that are either bisexual themed or feature bisexual characters (whether they use the term as an identity or not). Be forewarned: I'm also a fan of quirky characters, people who are outside gender norms and binaries, and non-traditional romance. If you're looking for something that's in the vein of Harlequin, features only traditionally masculine cisgender men, or is heavy on the explicit sex, you (mostly) won't find any of that on this list. I also don't care if the word "bisexual" appears as long as the author has handled aspects of bisexuality in a non-tropey or stereotyped way. For the majority of these books, a character simply is bisexual and doesn't feel the need to "prove" it by word or deed.
Since I'm a writer of m/m and m/genderqueer fiction, I do tend to read mostly m/m. If you are interested in f/f or f/genderqueer, there are probably better people to give you suggestions. In no particular order, here are some of my favorites:
1. My Zombie Boyfriend, by T. Strange:
Why I loved it: Hot nerd, creepy fun, bizarre bffs, oversharing parents, and a sexy, pretty zombie. What's not to love?
2. Down on the Other Street, by Jennifer Cie
Why I loved it: It's what I wish I'd been reading in my literature classes. Deep, and it made me think. There's a second volume as well.
3. Seoul Spankings, by Anastasia Vitsky
Why I loved it: I adored the characters, and I found the cultural details fascinating.
4. Temptations of Desire, by Tempeste O'Riley
Why I loved it: An exceptionally well-written genderfluid character. Very steamy sex.
5. Tangled Mind, by Posy Roberts
Why I loved it: Emotional, but well-drawn. Favorite bi-related line was a comment about how the love interest's bisexuality "confused" their friends. Truth.
6. Any Way We Want, by Grey Cole
Why I loved it: This was a good example of bisexual erotica that didn't feel overdone and misogynistic to me. Also, the author uses the word bisexual as an identity more than once.
7. Bowl Full of Cherries, by Raine O'Tierney
Why I loved it: One character calling out another on the tropey "gay for you" thing, but not having it actually be "gay for you" and being more self-discovery instead. Also, nicely addresses fat-shaming.
8. The Other Me, by Suzanne van Rooyen
Why I loved it: I loved reading about a trans boy. All the other trans YA I'd read was about trans girls. I enjoyed the overarching themes of grappling with identity.
9. Forever Burn, by Adrian J. Smith
Why I loved it: Action, a background love story, and strong women (rather than "Strong Female Characters," which is a bad trope). There are two companion books in the series, and all are worth reading.
For great reviews and more recommendations, be sure to check out the Bisexual Books Tumblr.