I do not have the Dread Thingonomicon, but I have a few other resources I hold in high regard from the same publisher (Raging Swan Press): GM's Miscellany Dungeon/Urban/Wilderness Dressing. Based on the previews of Dread Thingonomicon, I think it's a comparable product to the three others I own.
I do own the Tome of Adventure Design (and have used it in my game preparations), so I'm prepared to discuss that.
The GM's Miscellany line is full of immediately useful information: traps, random names for taverns, examples of descriptive text for portcullises/altars/more. There are examples of puzzles and riddles, charts of treasures, things found in garbage piles, etc.
What does Tome of Adventure Design have? Well, it's not as immediately useful. You're going to use it to brainstorm big campaign ideas. Like do you want to roll up the ancient history of a dungeon? The motivations of a villain? You can tell that it's been assembled piecemeal over a long period of time. There are charts that duplicate. Some of the charts are unclear of why you'd be rolling on them. You'll spend a good chunk of time on charts, rolling up vague (but evocative) names and descriptions).
So if you want something quick and to describe what you've already got, look at Raging Swan's products. If you have no idea what kind of story you want to tell and are starting from absolute nothing, take a look at Tome of Adventure Design.
In my games, I haven't really had a use for Tome of Adventure Design.
