I was just browsing for 'The Code Series' myself the other day! If you're looking for physical copies, big retailers like Amazon and Barnes & Noble usually have them in stock, both new and used. For digital versions, platforms like Kindle, Apple Books, and Google Play Books are solid options—sometimes they even have sales or bundle deals.
Don’t overlook indie bookstores, though! Sites like Bookshop.org support local shops, and many can order the series for you if they don’t have it on the shelf. I’ve also stumbled upon signed editions on eBay or AbeBooks, which feel extra special. If you’re into audiobooks, Audible might have narrations, though I’d double-check the narrator’s style first. Happy hunting—it’s such a satisfying series to collect!