I hope my insufficient Latin knowledge nevertheless can convey the proper meaning of this thread's idea: there are photography books which are not only useful, they are a condensed yet exhaustive repository of all that's really important.

Obviously, you can't put everything in a book, but some books succeed in reaching an apex no other work can. Here are the ones that I have digested/consulted:

  • Haist, Grant. Modern Photographic Processing. v.1 and v.2. John Wiley and Sons : 1979. 1442 pages.

I have actually read, though not necessarily always closely, that whole thing. It's perhaps the only book still in print covering both the principles and the engineering of B&W and colour film. We're down to the gory details here: numbers, curves, chemical equations, but also lore, mythbusting, and historical perspective. You could consider it as the biggest literature review of scientific papers on light-sensitive materials, coherently assembled into a readable narrative.

  • Mees, C. E. Kenneth. The Theory of the Photographic Process. MacMillan and Co.: 1942. 1124 pages.

Before Haist there was Mees: first director of the Kodak Research Lab, founder of the Wratten company (to whom we are indebted both filters and panchromatic sensitization), Mees is a towering figure. The driving force behind Kodak's technological and industrial domination during the first half of the 20th century, Mees reigns supreme among photographic scientists. This book is the consolidation of half a century of work on dry plates, and contains countless details on the properties of light-sensitive materials, the scientific principles underlying them, the modelization of their behaviour in mathematic formuale, and the means of their study. One glaring omission however concerns the manufacture of emulsion: to avoid disclosing trade secrets, nothing is said of emulsion-making. Even though it's a precursor to Haist (who was also the head scientist of the KRL, later on!), the angle is slightly different since the theory is more detailed than in Haist. Haist really covers everything, but Mees will go deeper into the experimental protocols. The chapter on the study of tone reproduction is particularly fascinating in explaining how they combined both objective and subjective criteria to arrive at the particular tonal compression we find most pleasing in B&W.

  • The Kodak Encyclopedia of Practical Photography. Amphoto: 1977. 14v

Not in print anymore, but your local library must have a set, and you can still buy it around online vendors. Worth reading for every photographer, budding or pro. Photo dictionaries and encyclopedia come and go, and are sometimes nothing more than mere rehash of the same stuff over and over, but Kodak's achieves that rare goal of being entertaining, technically rich (something other encyclopedias usually avoid), fully illustrated with lots of meaningful diagrams and photos, and accompanied by practical recipes/advice/guidelines. Contains one of the best explanation of Tone reproduction theory for the layman, demonstrating what the combined effects of lens, film, and paper do to image tones.

  • Focal Encyclopedia of Photography. Various editions

Although I prefer the Kodak one for its accessible style, the Focal Press Encyclopedia is also worthy of the Summa label. The 1969 desk edition I have is a dense, exhaustive survey of photographic tools, materials, and means, whereas the more recent electronic edition (2000-ish) is of a completely different style: more content is devoted to history, trends, aesthetics, and academic research on photography. The focus has shifted from the photographer to the Fine Arts student, but it acquired valuable scholarly information in the process. Although I love the old edition for its tables of now-obsolete formats, and oddities such as electronic printers...

Originally available as printed book, now famous as a PDF, this is a must read for beginning to understand the durability of colour materials, what makes them fade, the science behind it all, and what to do to protect your assets.

  • The Photo-Lab Index. Lifetime edition. Morgan & Morgan: 1977.

Huge compendium of formulae for developers, stop baths, fixers, toners, test solutions, washing aids, etc. Superseded in print resources by more recent compendiums such as the latest Darkroom Cookbook, but a touchstone for photographers over the years of its existence.

  • Rudman, Tim. The Photographer's Toning Book: The Definitive Guide. Amphoto: 2003. 208 pages.

This is the smallest book in this list, but it is worthy of the Summa label for being the only available book to cover in depth this narrow subject. Toning is always a topic in various books, but seldom (never?) has it been so thoroughly investigated, demonstrated, and taught as well as here. Required reading even if you just dip your prints in 1+19 KRST for "archival permanence." You might be surprised...

Phew! There will be more to come, but I'd like to encourage you to submit your own. Remember, we're not just talking about merely useful books here: we're talking about totalizing books. The kind that aims to harness ALL the knowledge about a subject (even if we know that it's patently impossible). The clearest omission from my list is a history of photography. I know there's about two really good ones in print, but most of the others are rehash of rehash of Newhall: dearth of original treatment is what keeps me at bay from most histories.

Add your own!