Lean Book: The Hitchhiker's Guide to Logical Verification [pdf]
For those on the fence about learning Lean or some other theorem prover: I highly recommend it if you want to self-learn math. Learning math from a textbook is rather dry and often doesn’t come with solutions.Lean essentially gamifies learning math and you always know if you got the right answer. Moreover, unlike written math which is rife with ambiguous notation (unless you’re an expert), math in a theorem prover like Lean is always unambiguous.