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.
That sounds interesting. Esperanto has no noun-declinations, it’s an agglutinating language, you don’t bend words (= declination).
But what is barely resembling that what you mention is the two cases of the language, which is nominative and the so called “accusative”. Which is adding -n to words to make them an object, depending on whether the verb of the sentence needs one or not. This case also is not just for objects, but also for directions, for measurements and time. That combination normally confuses the heck out of people.
Which is why there is also an in-joke in the Esperanto community “don’t forget the accusative”, because people forget it or apply it too often.