I just finished this book called 'How to Write Asexual Characters' from the publishing house, Salt and Sage Books. (I'll attach the link below.) I really enjoyed this book because it discusses what asexuality is, the spectrum of it, the stereotypical tropes, misconceptions about asexuality, etc. Again, highly recommend as it's a basic starter for people who want to learn more and don't know where to start. The read is super short (80 pages), so this length is a bonus.