It's a problematic adventure. The first level has some really inspired (and nasty) encounters on it, but there's also a lot of empty rooms without any descriptions at all. After that, the lower two levels aren't really that interesting - a few encounters that have potential, but a lot of rather boring material.
(It should be noted that some of it is also a very old dungeon indeed, predating the publication of D&D! The golem with the whip of cockatrice feathers is described in the original three booklets...)
What the adventure really needs is for you to make the NPCs mean something. Eli Tomerast is a fantastic villain if you actually give him something to do rather than skulk around the bottom of Maure Castle. As a "let's explore this dungeon" setting, which is how the adventure is framed, it lacks a certain something.
A few other levels of RJK's castle were published in 3E stats in Dragon magazine, as I recall. [MENTION=1613]grodog[/MENTION] could tell you where!
Cheers!