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Published April 2017 by Wizards of the Coast
Tales from the Yawning Portal is a collection of older AD&D and D&D 3.x adventures, and one D&D Next playtest adventure, converted to D&D5. It consists of:
The Sunless Citadel
The Forge of Fury
The Hidden Shrine of Tomoachan (originally C1)
White Plume Mountain (originally S2)
Dead in Thay
Against the Giants (originally G1-3)
Tomb of Horrors (originally S1)
The adventures aren't linked as a supermodule, with a common thread running through them, but they are set up in order of difficulty so you could start at 1st level in the first one and move your way up to finally challenging the modernized Tomb of Horrors at 12th level plus. Actually it doesn't set a level recommendation for Tomb of Horrors, but you're theoretically going to be 11th level when you start G3 so you should probably be at least 12th when you're finished with it.
The maps are beautiful and full-color, and not difficult to read in general - although the numbers don't pop out quite like they do in monochrome maps. My main complaint is that they aren't very large, and they're embedded in the text - lots of page-flipping to run this, unless you're going to make a full-color copy to work off of. Special areas with extra detail do get picked out with zoomed-in maps, however - White Plume Mountain especially needs and gets these.
Monster stats similarly need page-flipping - nothing get statted in their own encounter area - pretty typical for D&D5 adventures. Some monsters get special stats, however, modifying a typical entry. In actual play this seems like it would mean needing to write them both down in a combined stat list to facilitate play.
The art in the book is fantastic. It's very attractive, and like the originals, pictures a lot of special areas and encounters so you can just show people what they're seeing. I'd suggest supplementing them with the ones from the original modules if you have them, however.
In the conversion to D&D5, the numbers of foes often get reduced, sometimes dramatically. For example, there are 9 trolls in three connected areas in the the converted G3. In the original, there are 56 trolls in those three areas. Another area has 6 instead of 18. The sheer numbers you could deploy, and deal with, in AD&D are not the same in D&D5. I have no doubt those reduced numbers are still a challenge, but it's worth noting that this changes. Similarly, some monsters are downgrades - young hill giants fighting as orcs, not as ogres, stuff like that. They had to resort to some tricks to explain other things - such a dragon's lair becoming an extra-dimensional space to accommodate the physically muck larger dragons of D&D5.
Traps and treasure get downgraded a bit. Traps generally aren't the save-or-die, supra-tetanus of the 1st edition adventures and are usually more survivable. Or at less flat-out dependent on you having access to wishes and raise dead to undo your bad rolls. For treasure, that means some hoards are a bit smaller, magical plusses tend to be lower.
How is it for GURPS?
In a way I think the extra detail that comes with D&D5 (DCs for tasks, for example) and reduced numbers of foes makes them easier to convert to GURPS. Just add some magic to more of the encounters, make the monster tough by GURPS standards, and keep the reduced numbers (numbers are brutal in GURPS, too, in a way they aren't in AD&D) and have at it. The reduced but more detailed magical items suit GURPS DF in a way that the larger hoards of magic from AD&D don't quite.
Overall: I really enjoyed this one. The converted and updated adventures read almost exactly like the originals, they stay tight and focused, and they feel like the originals did. It was just a good read, and I really enjoyed reading the updates of the modules I knew by heart from my AD&D days and getting to look at ones I'd missed from after I stopped GMing D&D.
Recommended. Attractive and well done.