There are two published books that teach Lojban; The Complete Lojban Language and What is Lojban?. There is also an incomplete but substantial guide, Lojban for Beginners, which teaches Lojban as a course.
The Complete Lojban Language is a complete description of the artificial language Lojban. It serves as a reference grammar for the language, offering an overview of the language, as well as linguistic details on every aspect of the language. This book serves as the standard defining the language design. That design has been declared frozen for a minimum 5 year period; anyone who learns the language from this book can be assured that it will not be continually changing. Though this description may sound imposing, technical and formal, the book is written in a light, often humorous style that teaches the reader about the Lojban language, about logic, and about linguistics in general.
An online draft version of The CLL called The Lojban Reference Grammar is available. A list of errata is also available. Most of the errata have been approved.
What is Lojban? is intended as a concise introduction to Lojban, providing a taste of the language for those who may decide to take an interest in it.
Lojban for Beginners is an introductory course on Lojban, consisting of fifteen lessons. It has been authored by Robin Turner and Nick Nicholas, and gives a gentle introduction to the structure of the language. Robin authored lessons 1–8 and 10–11 in 1999; Nick added to the existing lessons, and authored lessons 9 and 12–15, in 2001. This book is very accessible, and interacts with the reader using relevant exercises!
ld.pdf is a Lojban-English and English-Lojban dictionary. This PDF version has some nice additions to the run-of-the-mill dictionary: