Lawrence Revere's book does a hatchet job on the Hi-Opts. It is a half truth. What Revere shows is that his Plus-Minus Count has a higher betting correlation than either Hi-Opt. This is because the Hi-Opt systems do not count the ace in the main count, but his system does. The ace acts as a high card for betting.
What Revere does not show is that the Hi-Opt systems have higher playing efficiency and insurance correlation than his Plus-Minus Count. This is because (1) the ace acts as a low card for playing efficiency and (2) a ten count has the best insurance correlation, while either Hi-Opt resembles a ten count more than the Revere Plus-Minus Count does.
High-Low also counts aces in the main count. Betting correlation is relatively more important for multi-deck games than for single deck games. Almost all single-deck games are 6:5 garbage today. Therefore, a new counter should learn High-Low, rather than Hi-Opt I. Hi-Opt II is an extremely effective system.
The World's Greatest Blackjack Book has correct basic strategy and the Hi-Opt I, but not Hi-Opt II. It also has superstitious nonsence like advice not to play against tough-looking dealers who wear a lot of jewelty. It has a betting system that is part count-based and part progression-based, but I think Humble and Cooper present it as a cover for counting, rather than because they think a progression-based system is the best betting system. The book vastly overstates cheating by the casinos.