A classic module, and an adequate DriveThru reproduction
(As of 31 January 2018)
About the PDF: Upon first release, the PDF of this module contained significant errors and omissions. As of late January 2018 a new PDF has been added which corrects those errors, and the full text of the module is now readable. The font and typography are still different to the original module, presumably as a result of making the text searchable (which it is) but this is a minor quibble. More disappointingly, the images are still much lower resolution than the original print copy, but the maps are legible and there is nothing that should stop the module from being run as originally printed.
The rest: Putting the poor scan aside, this is a classic AD&D 1e module, the first in the long-running original Dragonlance DL series of modules. You will need a set of AD&D 1e core books (Players Handbook, Dungeon Masters Guide, and Monster Manual) to use this. (Most monsters are provided with full stats but a few, including the dragon, refer back to the expanded descriptions in the Monster Manual.) No prior knowledge of Dragonlance or other Dragonlance supplements are needed - the module gives you everything you need to start a new campaign in Krynn.
The module provides about 15 hours of play, divided over three parts (if you stick to the key encounters), or significantly more if you use random encounters or players stray from the main quest path. Part 1 is an overland "hex crawl", although sadly there is little incentive for players to visit most of the included hex map as the shortest path from the start to Part 2 bypasses the majority of it. Part 2 and Part 3 detail the surface and undercity of the ruined city of Xak Tsaroth in a fairly traditional dungeon crawling format. Groups who successfully complete the module can continue the story in DL2, "Dragons of Flame".
Other than the fact it begins the long-running Dragonlance brand, DL1 is most memorable for some of its unique design decisions. The first is that the module asks you to use the pregenerated characters contained within, representing the Heroes of the Lance from the Dragonlance novels. These characters are wildly unbalanced, ranging from a level 3 wizard to two level 6 (!) fighters (one of whose stats are just better across the board than the other). There is no real reason you can't use your own characters, although later modules reveal Krynn's elves, dwarves and gnomes differ from the traditional tropes in ways not really explored in this module. Also, PC clerics will have particular trouble for reasons unique to the module's setting. A second standout point is an included song, with sheet music, plus a long poem. The module is illustrated with evocative professional art throughout, and of course modern players with Google also have access to the wealth of stunning Dragonlance art depicting many of these characters and encounters which TSR and Wizards of the Coast have commissioned in the years since.
The module contains several maps in colour, semi-colour, and black and white, and these have been faithfully reproduced in the PDF, albeit in lower resolution than the original publication.
What the module loses in solid game design, it makes up for in passionate world-building, and even at this early stage it's clear that Dragonlance is a product with a wealth of backstory and internal consistency.
The module as-written can be fairly easily converted for use with other editions of D&D other than Basic or 4E. An official simple conversion exists for 2E in a compendium with the next three modules, although as of this writing that particular item is not currently available through DriveThru. Sovereign Press did an exceptional conversion for 3E that significantly improves the modules, updating many elements of the game design to more modern sensibilities, and that one IS available through DriveThru, and forms a wonderful additional resource even for those wanting to run the module in its original form.