The book begins by explaining its history: the adventure was originally published as a solo gamebook in 1983 by Ian Livingstone, and has now been converted into a standard Dungeons & Dragons adventure suitable for a Dungeon Master and either one 8th-level character or a group of 6th-level ones (4 pregenerated ones are provided). While designed as a stand-alone one-off adventure, it would be possible to integrate it into a campaign... as the premise is that someone has built a 'test' dungeon and encourages people to try their luck in it, all you need do is allocate the role of the builder to some suitable individual in your campaign world and decide where he put it.
Speaking of 'luck' the next couple of pages are devoted to an addition to the rules, basically as the original gamebooks made extensive use of luck a set of luck rules for the D20 ruleset have been devised. It's something you'll either embrace wholeheartedly or decide not to be bothered with, it could - if you like it - add a distinctive spin to your whole campaign, while if you do not care for it, leaving it out will not make a significant difference to the adventure. This is standard text in all the 'Fighting Fantasy' D20 books.
Back to this book. The adventure starts with a bit of background for the DM and a 'read aloud' introduction for the characters - naturally if you have integrated this into your campaign you will have to amend this as appropriate, but there is sufficient here to make sense if you are playing a one-off. This is dungeon-delving as spectator sport, probably the best approach to take with this kind of 'dungeon-as-test.' The whole thing is quite coherently presented but it is very, very easy - as the designer intended - for characters to come to grief. It is very much a case of having to correctly deduce what you are supposed to do, and which items are important and which should be left alone... and most of the time there is no way to tell until it's too late! Such dungeons are very much a matter of taste whichever side of the DM's screen you are sitting: they can be highly enjoyable or so boring that characters look for ways to kill themselves so as to end the game... this one has the potential to be highly enjoyable provided that you enjoy the artificiality of a dungeon that's there to serve purely as a test of skill.
While it is intended to be run for either one character or a small party, several of the descriptions and encounters are aimed at a single person so a read-through beforehand and some thought about how to accommodate a group is advised for DMs playing with a party of characters.For example, without giving too much away there is a quizmaster type who asks riddles, but although he has taken precautions so that he only has one 'contestant' at a time, he only has one riddle! So if you have several characters, make sure you have some more, or take the player whose character is being quizzed out of earshot of the other players.
Dungeon completed, there are several new monsters - some of which will prove useful additions to your collection - and some new magic items. These all appear in the dungeon, but are given a complete write-up here, of particular use if you decide to use them elsewhere in your campaign. Talking of campaigns, there are notes about the city of Fang here, should you decide to include not just the Deathtrap Dungeon but its location in your campaign world, as well as notes for scaling the dungeon should you wish to run it at a higher or lower level than written.
Unless you want to amend the final room, I would recommend that this be used as a one-off adventure, or for a single character. That said, if you enjoy puzzle/test dungeons, this is a fine example!