Not the author, but it would take 2-3 weeks if you learn by yourself (to get real stuff done, not to be an expert), or 3 full days of hands-on training.
I would recommend Lamport's video course[1] and TLA+ hyperbook[2] (Lamport says he's stopped working on it, but it's fairly complete). Note that both Learn TLA+ and Practical TLA+ don't teach much of TLA+, but rather a language called PlusCal that compiles to TLA+. Some programmers may find it easier to start with because, unlike TLA+, PlusCal resembles a programming language (and like all programming languages, it is much more complex than TLA+, but more familiar). Hillel's book also contains some good real-life examples.
You can also find examples and various other links posted on the TLA+ subreddit[3].
"Note that both Learn TLA+ and Practical TLA+ don't teach much of TLA+, but rather a language called PlusCal that compiles to TLA+. Some programmers may find it easier to start with because, unlike TLA+, PlusCal resembles a programming language"
Most evidence indicates using familiar concepts aids learning. That makes me hypothesize the best recommendation is the more mathematical ones for folks strong in math and the programmer-centric ones for those strong in that. That also implies that, for each of these formal topics, we need one version for each audience to draw more people in.
Seem's like hillel's material is more approachable for people with a programming background, and pron's recommended material better for people who are more math-y. I'm likely going to start with Hillel's books to develop a working understanding and then move onto Lamport's stuff once i'm ready for a rigorous deep dive.
I would recommend Lamport's video course[1] and TLA+ hyperbook[2] (Lamport says he's stopped working on it, but it's fairly complete). Note that both Learn TLA+ and Practical TLA+ don't teach much of TLA+, but rather a language called PlusCal that compiles to TLA+. Some programmers may find it easier to start with because, unlike TLA+, PlusCal resembles a programming language (and like all programming languages, it is much more complex than TLA+, but more familiar). Hillel's book also contains some good real-life examples.
You can also find examples and various other links posted on the TLA+ subreddit[3].
[1]: http://lamport.azurewebsites.net/video/videos.html
[2]: http://lamport.azurewebsites.net/tla/hyperbook.html
[3]: https://www.reddit.com/r/tlaplus/