Agreed. I think the problem with Douglas Adams is he just didn't know how to frame things in a way that didn't get dismissed as trite. Jonathan Swift had the same problem; nobody got the comedy in "A Modest Proposal" so they sure as shit didn't get the political message.
Maybe he didn't live long enough to make the transition from pure comedy to writing something else. In a lot of his essays and letters he showed a sublime, tragic understanding of the world which reminded me of some of the greatest novelists of the late 19th/early 20th century. Last Chance To See was a start.
Bump it up if you can. It's heartbreaking, and it doesn't feel anything like Adam's books. Honestly, it feels like a conversation with the man himself - it's witty in an offhand, unstructured way. It's sad and beautiful and doesn't have the "pat" feel that gets some much of the rest written off as juvenile.