There are a whole lot of PDF e-books here: http://i-espero.info/files/elibroj/
They include La Mirinda Sorĉisto de Oz and others in the series, Alicio en Mirlando and Trans la Spegulo, as well as the older version of the story (La Aventuroj de Alico sub la Tero), Kristnaska Kanto and La Batalo de l' Vivo, and many others. They seem to be primarily translations, but there may be some originals (I haven't opened every one to verify). However, they are done by an assortment of translators, and the translations vary in quality from excellent in grammar and style, to ones that contain quite a few grammatical errors and are mediocre in style.
Also, the page consists entirely of PDF links (title and author being indicated in the file name) marked with their file size, so no info on the nature of the book, the identity of the translator, whether it's translated or original, etc. So you have to open the file to get any additional information.