A classic of English grammar, Essentials of English Grammar provides a common ground for the traditionalist and the structural or descriptive linguist. Jespersen’s work provides insight into the fundamental concepts that underlie the linguistic approach, but at the same time the foundation of the traditional approach is retained.
I'm pretty sure this is not the edition I read, but I would be at a loss to say exactly which edition I DID read.
This is a very hard book to get through. Jespersen doesn't spare his readers, and it would be a mistake to approach the work without a very thorough grounding in the history and structure of the English language.
With that background, the book still isn't easy reading. But it's the most thorough grounding in English grammatical and phonetic principles available, and repays the effort.
But it would probably be more useful as a reference than to read right through, which is often the case with dictionaries and grammars.