I really, really like Step By Step in Esperanto by Montagu Butler. It's the best introductory textbook of any language that I've read. It's composed of maybe

I really, really like Step By Step in Esperanto by Montagu Butler. It's the best introductory textbook of any language that I've read. It's composed of maybe ~1000 or so very short lessons (each is about a paragraph), so it makes it very easy to make a little progress every day even if you only have a couple of minutes before bed. There's a nice mix of reading, translation exercises, pronunciation exercises, and grammar.