New to UX Writing? Give these resources a read.
Microcopy: The Complete Guide by Kinneret Yifrah. A great intro into how to handle error messages, toasts, and other basic components. Also some good explanations on voice vs. tone.
Thinking with Type by Ellen Lupton. This is more of a design book, but understanding the principles of design makes team collaboration a heck of a lot easier.
Meander, Spiral, Explode by Jane Alison. Again, not a UX book, but a great insight into the craft of writing. This book explores how storytelling can take many routes; UX writing usually needs to take the straight and narrow path, but thinking in terms of plot can help keep your eyes focused ahead.
On Writing Well by William Zinsser. If you've been writing for any amount of time, you probably know this book. Always a good resource on basic writing principles, especially grammar and clarity.
Because Internet by Gretchen McCulloch. Internet language has different rules than spoken language. That doesn't mean that UX should be sprinkled with "lol's," but it can help you get into the "write it like you say it" mentality.
Writing is Designing by Michael J. Metts. A great argument for why writing needs to be part of the design process, not just an afterthought.
Forms That Work by Caroline Jarrett. Nothing worse that a complicated form. These basics can rid the world from those bureaucratic nightmares.
About Face: The Essentials of Interaction Design by Alan Cooper. This delves into the value of user research, as well as some fundamentals for mobile design.
The Psychology of Everyday Things by Donald A. Norman. Even a door can be confusing if it's not designed correctly. This is a must-read if you're needing an intro on information hierarchy and clear affordances.
Don't Make Me Think by Steve Krug. The main idea behind this book is that the cognitive load caused by your interface should be as low as possible. AKA: write clearly and give users what they're expecting.
The Elements of Style by William Strunk Jr. Another writing classic. Like On Writing Well, it's more grammar-based than other books on this list, but still a valuable and short resource.
Everyday Information Architecture by Lisa Maria Marquis. If you only read one book on this list, consider this one. Not only should your writing be clear, but it also needs to be in the right place.
The Copywriter's Handbook by Robert W. Bly. This is one of the longer books on this list, and mostly deals with traditional copywriting (advertisements, direct mail, etc.). Still, it goes through some fundamentals on grabbing attention and improving click rates.
Shady Characters by Keith Houston. Okay, yes, I snuck a typography book on this list. But I promise it belongs here: Typography is all about design, functionality, and what happens in our brain when we see certain symbols. Steal Like An Artist by Austin Kleon. If you've ever dealt with impostor syndrome, start here. UX Writing isn't based on plagiarism, but researching similar products, following your favorite writers, and letting yourself be inspired but other work is a good thing. And here's a quote for free that I keep posted on my desk: "Validation is for parking."