Reddit mentions of Improvisation at the Speed of Life: The TJ and Dave Book

Look to the right of your screen and down a little bit.

Based on your recent post, I feel like you're looking for a training program in book form. The UCB Manual is the most comprehensive and closest thing to that, but take it all with a grain of salt as at a certain point it does start teaching the UCB style. Novices may take some things to mean these are this-is-the-only-way-to-do-things hard and fast rules, but it's just the way to play their aesthetic. Be open to other possibilities.

Some books, like the recent Will Hines book or Napier's Improvise, are very good but I recommend them after you've done a bit of improv. Same with this, this, and this.

Johnstone's Impro is great for a peek into story-based
British style improv. His passages on status are invaluable.

I personally don't care for Huack's Long-Form Improv, mostly because at the beginning of the book he tries to distill all improv comedy down into an equation, which is way too simplified for my tastes. Improv Wins is a decent, breezy book, but I don't like how they pose scenario questions and then suggest that there is a "correct" response you should make. Still, if you can glean insight from a book, even an understanding of disagreement, then that makes the book valuable in some way.

The only real way to learn improv is to do it and not be afraid to make mistakes and missteps along the way. You will not get improv right the first time.

• Upright Citizens Brigade Comedy Improvisation Manual is usually the first one that people speak highly of. Half of it is theory, and the other half is exercises. I find it the most solid gathering of tactics, but maybe a comparison to other schools would help me understand why their “game” makes them so different.
  
• Improvise: Scene from the Inside Out by Mick Napier is probably the next best one on my list. It personally resonated with me because the idea of “take care of your partner by taking care of yourself” identified one of the less-spoken of but more critical parts of improv. I’ve been in many scenes where the who/what/where slips through the cracks because we were too polite to not make a bold choice and each of us were scared to decide what the scene should be about. If each of us collectively decides individually and “yes, and,” we’re on a really good trajectory.
  
• Improvisation at the Speed of Life: The TJ and Dave Book is my long-form inspiration. You get a lot of mindset here, not as tactical as the others.
  
  Interestingly, this one blog post “How to Be a Better Improviser” is actually a brilliant distillation of the most important concepts.
  
  It goes without saying that without practice reading alone will have limited utility.

Improvisation at the Speed of Life: The TJ and Dave Book by TJ Jagodowski, Dave Pasquesi and Pam Victor