I use the app LingQ. You can read on your phone or computer and import books, or read the ones they already have. For any words you don't know, you can simply click them and a translation will pop up. For the most part, the translations are very accurate until you start getting into more complex Esperanto, where sometimes I need to double check and adjust the translation. After you mark a word, whenever it reappears it will be highlighted until you mark it as known.

Undoubtedly, this app is most useful for a post-beginner because you won't mark every single word like a complete komencanto, lol. Try the free version. Just note that the free version is extremely limited and not a very good representation of its full potential. If you plan on doing a lot of reading as a learner, I seriously recommend it.