This book was converted from its physical edition to the digital format by a community of volunteers. You may find it for free on the web. Purchase of the Kindle edition includes wireless delivery.
It does what it says on the cover, and well. It is a thorough guide to Esperanto grammar which covers every prefix, suffix, root, preposition (etc.) so many times that you can't help but remember some of them! It also covers translation between English and Esperanto, as well as a ton of useful words and phrases. Yes, it's pretty dry, and some of the ideals represented in the examples therein are dated nowadays, but I didn't expect anything else from this kind of thing really.