Dragon Manual

 The Dragon Manual (also known as the Book of Dragons) is the viking encyclopedia of all dragon species discovered by the Hairy Hooligans tribe. Considered an important piece of knowledge, it is how the Vikings of Berk know the weaknesses and methods needed to take down some of their reptilian attackers. After Hiccup and Toothless defeat the Red Death, it is given to him and his newly founded Dragon Training Academy to improve upon the content of the book and better the relations between vikings and dragons

Appearance
The book's cover is made of clean-pressed leather branded with the Berk crest on the front. The pages are pressed and yellow with age, containing elaborate illustrations and writing. As explained, the book has been in the possession of the Hooligans for many generations, it's curent physical state showing the care taken into preserving the book.

Lore
Over the course of his life, Bork the Bold (who at the time was called Bork the Very, Very Unfortunate and Gobber's ancestor) and his girlfriend attempted many professions, but was always sabotaged by passing Dragons. Over the years, Bork accumulated knowledge about the Dragons he encounters, writing the information down in a book. It was Bork who devised the Dragon Classes, and his work was passed down and modified through the many the Viking generations of Berk. His gathering of Dragon knowledge in spite of the risk to his own life merited his change of title. Whatever is not in the book of dragons, whether they are notes, personal thoughts, feelings, fears, recipes or "interesting sketches of his neighbors, are all kept in a chest, originally kept by Gobber and given to Hiccup for safe-keeping.

As Fishlegs has read the book over seven times, he has been known to spout facts from the book on many occasions, hinting that much of the content in the book (fire, venom, jaw strength, etc.) is described similar to that of the stats found in a modern day roleplaying game.

The book is categorized and defined in seven classes: Because of Berk's (and all other vikings, for that matter) contingency to kill dragons, every page both describes the violent and grotesque tendencies of the book and states "Extremely Dangerous. Kill on sight." The only exceptions to this are the Red Death (to whom neither Borg or any other viking has ever witnessed), the Typhoomerang (discovered by Hiccup and named by Fishlegs) and the Night Fury, who lacks any facts or description, instructing the reader to "Never engage this Dragon. Your only chance; hide and prey it does not find you." After the construction of the Dragon Academy,
 * Stoker Class - Hotheaded fire breathers, and most of them are capable of setting themselves on fire or possess their own, specialized form of using fire. Examples of this includes the Monstorus Nightmare, Terrible Terror, and the Typhoomerang (the first dragon to be discovered by the dragon academy). Hookfang represents this class in the Dragon Academy.
 * Boulder Class - Boulder Class dragons are tough and associated with the earth. They can eat rocks, and despite that their wings are smaller compared to their entire body, they are able to fly as fast and as high as most other dragons can. Examples include the Gronkle, the Whispering Death, and the Screaming Death. Meatlug represents this class in the Dragon Academy.
 * Sharp Class - Sharp Class dragons are vain and prideful, and they all possess sharp body parts. Examples include the Deadly Nadder, the Timberjack and the Speed Stinger. Stormfly represents this class in the Dragon Academy.
 * Tidal Class - Tidal Class dragons live in and near the ocean, and unlike most dragons, they don't have fire breaths as their ranged attacks. These dragons are generally bigger in size than most of other classes, consisting of species classified in the large Dragons. Examples of this includes the Scauldron, the Thunderdum and the Oceanzap. Though this class isn't technically represented in the Dragon Academy, Stoick does ride on his Thunderdrum Thornado.
 * Fear Class - Fear Class dragons are stealthy, sneaky, and often (but not always) have multiple heads.  Instead of fire, they breathe gases with different effects. Examples include the Hideous Zippleback, the Snaptrapper and the Flightmare. Barf and Belch represent this class in the dragon academy.
 * Strike Class - Strike Class dragons are most powerful, super fast, have pin-point accuracy, highly intelligent and have incredible vice-like jaw strength. They are also the most difficult to train, but the most loyal once trained. Examples of this class include the Night Fury and the Skrill. Toothless represents this class in the dragon academy.
 * Mystery Class - Mystery Class dragons have little known about them. Examples include the Changewing, the Boneknapper, and the Smothering Smokebreath. The Night Fury was once apart of this class, but was later placed in Strike class after Hiccup befriended Toothless. Though not officially represented in the academy, the Red Death can be considered a Mystery Class dragon.

In the TV Show, it is shown that the Screaming Death is not in the book of dragons. However, later on Hiccup states that Bork's notes explain that a Screaming Death only hatches once every on-hundred years. Whether or not this was not included in the Book of dragons from Borks notes (presumably calling it a different name), Fishlegs overlooked it out of sheer terror or a faux-pax from the TV show's writers is unclear.