Back when it was published, it was a decent alternative to the classic ECO from Chess Informant, which was a pretty massive 5 volumes collection; this uses almost the same style to present the table of variations, but is condensed into one volume.
Apart from a brief introduction for every opening, the rest of the annotations are only symbolic, so the instructional value is fairly limited. It's difficult to assess how much the lines suggested for all systems are still playable/stood the test of modern engines, but even assuming they are, this format of opening reference with little to no text, is pretty much obsolete now compared to a simple database.
Still, it is worth a 3rd star for being, at the time, an improvement over the BCO2 volume published a few years earlier, and more practical to the club player than the full ECO
