I'm a completist. So this book is for me. If you are not a completist, this book is probably not for you.
Williams' first book is.... fine. It's fine. It's insightful, poetic, dreamy. But it's of a different stripe to his later three masterpieces. It's overwrought, looser, less focussed at the sentence-level (though more focussed on the narrative level). The writing isn't as satisfyingly precise and beautiful. It's amorphous, struggles to be poetic. I would suspect that's why William's largely disowned it - the easily recognisable youthful struggle for importance and poeticism.
It's fine, but it's not worth going out of your way for. The majority of readers will miss nothing if they only read his three major works. But, as I say, for completists, this is an interesting curio that isn't bad.