I've been obsessed with Larissa Ione's books ever since I stumbled upon 'Pleasure Unbound' in a used bookstore. Her Demonica series is my guilty pleasure, and I've hunted down her books everywhere. The easiest place to get them is Amazon—both Kindle and paperback versions are usually available, and they often have deals on older titles. For physical copies, Barnes & Noble usually stocks her newer releases, and their website has a solid selection of her backlist.
If you're like me and love supporting indie bookstores, Book Depository is a great option because they offer free worldwide shipping. I've also had luck finding signed copies at Powell's Books, though those tend to sell out fast. For ebooks, Kobo and Apple Books often have her full catalog, and sometimes you can snag discounts during sales. Don’t forget to check out her website for direct links to retailers and occasional signed book giveaways!