Erudite may be referring to generally well-read. Anyway, the sentence reads ok to me fwiw.

I'd agree, except it reads to me as "many of the erudite readers _of this_ little book", it seems to imply erudites of Darwin's book.

"this little book" refers to "The Nation of Plants" - from which this piece is an excerpt. It's probably more obvious when you're holding the book, as opposed to reading an excerpt on the internet.

Well, in that case I stand corrected :) It makes sense.