"Best writing books". Hmm.
I guess you are looking for insight and a spark for your own writing. Maybe wondering how anyone managed to write anything!? The practicalities, the process, the mentality. Are you writing fiction, poetry, both, something else?
I have sought out, collected, owned, dipped in, deep read and returned to most of the all known books on writing - Julia Cameron, Anne Lamott, Natalie Goldberg, King.. there are so many and they are like an orchard with so many ripe quotes you can pocket... most you will forget, a few you might carry around with you. I definitely went through a long phase of looking for answers, knowledge, motivation and inspiration. I've come round to thinking that not only is that looking in the wrong place it's also looking at the problem (of writing) the wrong way - this is honestly just the place I have reached...and been paused at for quite some time. I think the books were a distraction, a displacement activity - it's a comfort to curl up on a chair and "speak" with someone of the same mind and as I said - you pocket a few things along the way so I think other people are probably going to get different things from different writers so - I suppose reading around is worth it but it's like panning for gold - how mercenary are you, can you use enjoy the Zen of searching? I do think you can waste time and energy on books about writing - I sometimes jokingly say that I can sum up all the books by saying that al you need to do is get your actual pen on your actual page and bloody write something. I've been teaching myself Spanish for a while from books and apps but the truth is - the best way for me to learn is to actually speak it. Like swimming - you can read about technique and breathing and interval training but - you can read all you like - you really need to jump in the water and swim; do it - experience is the best teacher and all that.
Surprisingly perhaps - I am going to name a book but first there's a couple of other small things I want to put on the table - things that shaped my POV. One question that was asked in one of these books was "Why do you want to write?" - I kinda skipped over it at first because I have always done creative things - not just writing and other things in creative ways. I realised it was an important question to have thought about more deeply - I'm not going to bore anyone (any longer) with the answers I came up with for myself as they're deep, personal and complicated but I'm happy that I really thought about this - it could be a topic in itself: I think it's a worthwhile thing to do. It is just to plump up your plumage and peacock around - "I'm a writer, don't you know!" and "I have a book in print."? Hopefully the reasons run deeper than that. It matters to me that I have, in my own mind, a good understanding or the reasons and motivations to write. I think that if you've only got as far as saying that "you want to write" - I think it's worth digging deeper - that ability to dig deeper is, I think, a really important quality for anyone writing anything. So - this is an answer you won't find by reading anyone else's books - you have to search for in inside yourself.
I also gained something really important from reading the letters and diaries of Sylvia Plath and it was something I was not expecting. Have you ever wondered about what writers do when they are not writing? Or about how they write when they are not working on something? I've chosen Plath but it could be any author you find interesting - I read some of Ted Hughes letters too. The thing that dawned on me, and it's something I now carry with me and practice - is that Plath is very experimental and playful when she's writing casually - dashing off postcards and letters - she just flows and flowers on the page - it's so free and unselfconscious - all for a private audience of one; the way I read this is that she's, in effect, practising the art of creative writing every time she puts her pen on a page - a post-it note, postcard, a shopping list, anything and everything - for me this was a really valuable insight into the mind and practice of a writer - take a look at this postcard and see if you can see what I see.
FABULOUS FRACTURED FIBULA
So before I name one book and importantly the ideas it contained that made the most difference to me - here's a couple of others - both by Dennis O'Driscoll.
The Bloodaxe Book of Poetry Quotations- an extremely well structured book you can search and dip into when you are idling or stuck in a moment.
Like letters and diaries, I've always found interviews with authors like Seamus Heaney, Simon Armitage, Ted Kooser (all poets) a potent source of valuable ideas. The second O'Driscoll's book "Stepping Stones" - Interviews with Seamus Heaney - is one I've always enjoyed. My point is - that these informal writings and conversations are something that speak to me far more than many "books on writing". I've written songs based on interviews and documentaries where I've been inspired by the raw charisma of John Lennon and Marlon Brando - I find something magical in the way they speak informally.
So (finally) the book (or rather the ideas in it) that made the most difference to me is
A book on Creativity and Flow by Mihaly Csikszentmihalyi
So - once again - I'm pointing to finding answers to "the problem" of "writing" though self examination, self awareness - by looking at the whole problem through a different lens. If you're not already acquainted with the idea of a flow state you'll probably recognise it when you see it described - it's a state where you loose track of time, are very absorbed in what you are working on, blinkered, ideas come so quickly you can barely write then all down, you quickly and effortlessly make new connections and introduce new elements and find solutions to problems that were holding you up, you are very open to new ideas - in fact - I'd say (they say) it is a very enjoyable state to be in -(for me - probably one of the main reasons "to write") I always compare it to a big wave - I always try and surf it until the wave peters out. The question is always - "But how do you get into this state?" There's no one clear way - I can say I know and understand (generally) how it arises for me - I'm aware that things have caught my attention and keep bobbing to the surface, they refuse to go away - I start to pay attention - it takes time for ideas to knit together subconsciously until they reach some critical point where I feel the need to put something into words (this is a cut down version of what goes on for me). What I'm suggesting is that - with this understanding of the creative process, of the importance of the "flow state" - it's useful to hone your self awareness skills about how your mind works, what the creative process is like for you - once again - you are finding your own uniquely characteristic answers - but not from a book on writing. Csikszentmihalyi is IMHO (widely regarded as) the most important writer on "creativity" - so I'd suggest reading about "creativity" in general. I have an alert set up on google (log in to any gmail/google account you have using your browser and go to www.google.co.uk/alerts - set up a search term to be notified (emailed) about any new articles - generally scientific articles - about creativity - there is a lot of research interest in it.
HTH