This and Funk & White should be issued to every child entering primary school.
How to Keep Your Volkswagen Alive; A Manual of Step-By-Step Procedures for the Compleat Idiot by John Muir.
I bought this book before buying my Beetle, and it helped me overcome an ignorance of cars that bordered on technophobia. While I never progressed to the “I overhauled my engine by myself” level that other users achieved, I learned plenty that helped me, not just with the Bug but with every vehicle I’ve driven since. And it’s just plain fun to read!
Pocket Ref. Accept no substitutes.
Also, On Writing.
Programming Perl (the camel book.) Well laid out, has everything you need, and works at both the basic and advanced levels. Have it on my desk at work and it jogs my rapidly deteriorating memory.
The Complete Joy of Homebrewing by Charlie Papazian. THE bible of homebrewing. Read it cover-to-cover before I began brewing, and have used information in it every time I’ve made beer, wine, mead or cider.
I’ve put a few of these on my wish list.
London A-Z.
The Straight Dope 
The Pathologic Basis of Disease by Robbins and Cotran. It helped me pass boards.
What, no mentions of “The Joy of Cooking?” It used to be standard issue when you left home. Mine: “Auto Repair for Dummies” which, iirc, was actually the first book in the series. I learned cars and bikes working on beaters as a kid, and this really filled in gaps in my knowledge. “Zen To Go” by Jon Winokur, interesting collection of quotes from pop culture figures and zen masters about it’s fundamental principles.
In Search of Wonder by Damon Knight. It taught me how to write better science fiction and showed me the pitfalls to avoid.
Geneen Roth’s Breaking Free from Emotional Eating. It taught me how to eat like a normal human being. What can possibly be more useful than that?
Probably my rhyming dictionary. I’m an author and about half of what I sell is poetry for kids. I’d mention the title but I’ve misplaced it.
This bookmade me the grill master I am today -
[QUOTE=Low and Slow]
Step away from the propane tank. Surrender all of your notions about barbecue. Forget everything you’ve ever learned about cooking with charcoal and fire. It is all wrong. Get it right with the “Five Easy Lessons” program. Includes over 130 recipes and step-by-step instructions for setting up and cooking low and slow on a Weber Smokey Mountain, an offset smoker or a kettle grill.
[/QUOTE]
Even if you consider yourself a grill master - the rub and marinade recipes contained within are worth its price.
Final Cut: Dreams and Disaster in the Making of Heaven’s Gate
A stunning and cautionary tale. When one works in the film industry, one can come to the conclusion that ones shit does not stink. This includes crew.
I read this every few years. Keeps a cameraman humble.
Shirely you can’t be serious.
The Jazz Piano Book by Mark Levine.
Changed my life as a jazz and creative musician. Took 4 years of classical theory and made it all fall into place as I worked through the book. And I’m a bassist, primarily, although I do play piano as well. But I think like a bassist. Nevertheless, best single book I’ve ever bought.
About 35 years ago, I bought this because I was living on my own and about to buy my first house. Darn if it didn’t prove to be more than worth what it cost me!
My house was old, heated with radiators fed by an oil-fired boiler. The first winter, the radiators on the second floor barely got warm, and the ones on the first floor weren’t a lot better. So I pulled out the book and learned that the weird key thing I’d found in the house was used to bleed air out of the radiators. I figured out where to turn the supply water on, and starting on the second floor, I went around with a pitcher and the key, listening to the air rush out of the radiators till a stream of water came forth. It took maybe a half an hour to bleed the entire system, and in no time at all, the whole house was toasty warm.
I have no idea what it would have cost to have a repair guy deal with my no-heat situation, but I saved it because of my wonderful book!! 
It’s been handy since then, altho my husband is a much better resource now.
Secondly, two books come to mind: The Craft of Photography by David Vestal and Possum Living by Dolly Freed. Vestal is a great source for a lifetime’s experience in analogue photography and Dolly was a wayward teen writing a kind-of underground guide to DIY off-the-grid living long before it was fashionable (she married and today she works in aerospace in Houston) or even profitable.
Well, this probably won’t be very useful to many people here, but I refer to The Art of Electronics more than any other book in my library.