There are two massive reasons to like and admire this series.
1. The characters. The solid, thoughtful Inspector Gently is perfectly matched against his hot-headed subordinate Bacchus. I love both these personalities, and the way their peculiar, very 1960s outlooks interlock. Bacchus in particular is a really great creation, because he's likable in spite of his obvious faults.
2. The fact that it's ABOUT something. These are not just mindless whodunit puzzles. Each episode of the show has a strong point to make. In fact, multiple points. About how attitudes have evolved, during and since the 1960s. About human nature. About the law, and policing. This is a show that works as a police procedural, but also works extremely well as drama.
Apart from those two strengths, the show has atmosphere, a unique style, great dialog, and seething emotional confrontations. It's thoughtful, yet never slow. In fact, it's good on every conceivable level, including many that are rarely present in mere TV entertainment.
In short, this is one of the best cop shows ever to come out of the UK. Or anywhere else, for that matter.