Hey — if you want to buy light novels in English legally, I’ve got a little roadmap that’s saved me from sketchy sites and unbelievably delayed shipments. In the US and UK you’ll find most of the big releases handled by publishers like Yen Press, Seven Seas, VIZ Media, Kodansha USA, Vertical, and Square Enix Manga & Books. I usually start on the publisher’s storefront to see what's officially licensed; they often list release dates, ISBNs, and where the print and ebook editions are sold. Big retailers like Barnes & Noble and Amazon carry many titles in print and on Kindle, and chains sometimes have special editions or pre-order bonuses.
For digital copies I always check BookWalker Global first — they sell official English ebooks (and run frequent sales and point promotions). J-Novel Club is another great place: they release a lot of titles digitally first, often via subscription-style access and then help get popular series into print with partner publishers. Kobo, Apple Books, and Google Play Books are also reliable if you prefer DRM-protected ebooks outside of Amazon. If you like supporting the industry more directly, buy from the publisher/shop or use Right Stuf Anime for physical stock; they run good pre-order discounts and bundle deals.
Libraries are a fantastic legal route too: OverDrive/Libby and Hoopla sometimes carry licensed light novels, so you can borrow official releases. For older or out-of-print volumes, AbeBooks and eBay are decent for used copies (still legal purchases). I always scan for the publisher logo or translator credit to make sure it’s licensed — supporting official releases keeps my favorite writers and illustrators working, and that makes me feel good when a new volume finally arrives on my shelf.