Best version of 5e. Some of the things that really sold the game for me were:

• Game actually gives you concrete and solid exploration rules for both hexcrawl and point-crawl
• Different areas of gameplay are codified really well
• Power level is tuned just slightly down without losing compatibility with 5e
• Monster list is condensed and usable at the table

There were two things that bothered me. First, XP based on damage received/dealt is way too cumbersome and should be rewritten completely. Fortunately there are two other ways to award XP. Second, the demihumans are objectively better at everything compared to the core classes so I wouldn't use them in the same campaign. There are also some typos which should be addressed, but generally the books are well-written and laid out.

Overall, ItU is highly recommended for anyone willing to keep running 5e but with old-school tone. I'm really looking forward to the Companion expansion.