As anyone who has studied Esperanto for any amount of time will know, its grammar can be mastered very, very quickly. The hardest part of learning Esperanto is picking up vocabulary. A simple vortaro (dictionary) does the trick, but it's set up alphabetically, not categorically, so that won't help if you want to learn groups of vocabulary words at once, such as how to describe the world around you, or the names of various animals. You can also pick up vocabulary by going through a course like Gerda Malaperis, which I strongly suggest you check out. It's rather slow, though.
There's another option, however. Esperanto Self-Taught with Phonetic Pronunciation, by William W. Mann. This book focuses almost entirely on building vocabulary. And unlike a dictionary, it is provided according to categories. So you'll have a bunch of words for describing the world, and then animals, and then colors, times, seasons, and so on.
Better yet, it's available as an audiobook from LibriVox. This way you can download the mp3 files and build your vocabulary on the go and improve your ear for the language at the same time.
And while we're on the subject of audiobooks, there is an Esperanto translation of Alice's Adventures in Wonderland, one of my favorites, available on LibriVox as well. La Adventuroj de Alicio en Mirlando. If you're a fan of Charles Lutwidge Dodgson, aka Lewis Carroll, then you'll enjoy using this classic to train your ear to the sounds and rhythms of Esperanto.
Well, that's all for now.
Ĝis!
Links:
Gerda Malaperis on Lernu: http://en.lernu.net/kursoj/gerda_malaperis/
Esperanto Self-Taught on archive.org: https://archive.org/details/esperantoselftau23984gut/
or buy a hard-copy from Amazon: http://www.amazon.com/gp/aw/d/B003YL4OWM?pc_redir=1404824661&robot_redir=1/
LibriVox Esperanto Self-Taught Vol. 1: https://librivox.org/esperanto-self-taught-with-phonetic-pronunciation-volume-1-by-mann-william-w/
Vol. 2: http://librivox.org/esperanto-self-taught-with-phonetic-pronunciation-volume-2-by-william-w-mann/
Vol. 3: http://librivox.org/esperanto-self-taught-with-phonetic-pronunciation-volume-3-by-william-w-mann/
La Adventuroj de Alicio en Mirlando: https://librivox.org/la-aventuroj-de-alicio-en-mirlando-by-lewis-carroll/
