Every book is not "accessible", when it's not even opened and willfully ignored of existing.

There is:

• https://lernu.net
• [https://esperanto12.net/en](Esperanto in 12 days)
• [https://www.amazon.com/Complete-Esperanto-Learn-write-understand/dp/1473669189](Complete Esperanto)
• [https://en.duolingo.com/course/eo/en/Learn-Esperanto](Duolingo Esperanto)

There are languages to which it's less accessible, but from the bigger ones, it's quiet accessible.

But if people don't open their eyes they don't see the forest in which they are standing.