I have been consulting (and collecting) artist manuals for about 25 years. When I was an art student in the 1980s, I used them to learn about different techniques. Later, I became an art store clerk, and we kept a shelf of artist manuals behind the counter to answer customer questions about how to use the materials we sold. A few years later, I began my studies to become a conservator and again turned to artist manuals as part of my scholarship. Prior to conservation treatment, we carefully examine the objects that come into the conservation lab. Two important questions we seek to answer during examination are: 'how was this made?' and 'what materials are present?' Although we may not know for sure that a certain artist consulted a certain manual, they provide important clues. In a way, these books tell a story about the history of art from the point of view of the practitioners.
One early artist manual dates to the 15th century. Titled The Craftsman's Handbook in English and Il Libro Dell'arte in Italian, it was written by the artist Cennino Cennini and describes the methods and materials used at the time in the creation of drawings, frescoes, panel paintings, illuminated manuscripts, and more. Prior to the 19th century, artists had to make their own art supplies, so it also contains recipes for making brushes, tools, paints, vanishes, etc, and for preparing paper, boards and other supports. The book has an extensive discussion of pigments (some of which are still in use today) in which the author explains what was known at the time about its permanence, health effects, the kinds of imagery it is suitable for, and how well it mixes with mediums. Also fun to read are the bits of philosophy, advice, and flowery language mixed in with the technical information. The 1933 translation into English, by Daniel V. Thompson, is still in print today.
There is another, even earlier, manual titled On Divers Arts, subtitled The Foremost Medieval Treatise on Painting, Glassmaking, and Metalwork, authored under the pseudonym Theophilus. It was translated into English for the second time in 1963 by John G. Hawthorne and Cyril Stanley Smith from copies of the original manuscript, since the actual original is longer in existence. Both of these books encapsulate the point of view and body of knowledge held by artists of the time.
In my opinion, the most useful and comprehensive artist manual is The Artist's Handbook of Materials and Techniques, by Ralph Mayer. First published in 1940, it has been updated four times, most recently in 1991. It is a very good 'how-to' guide to different kinds of drawing, painting, and printmaking and sculpting. People have complained that it is out-of-date today, although many of the techniques described have been used for generations and will likely continue be used well into the future. However, I'm sure that if there is ever a posthumous updated sixth edition, it would be very well received.
A manual that has been updated more recently is Ray Smith's The Artist's Handbook. The most recent edition, published in 2009, describes traditional art techniques, as well as more contemporary practices, such as digital photography and digital image manipulation. It makes a good companion to the Ralph Mayer book. While Mayer has more text, the Smith book has excellent illustrations. Another example of where they complement each other is in the pigment charts. Some of the information is duplicated, but Mayer shows the spectral curves for each color and Smith highlights the chemical structure.
The Art Forger's Handbook, by Eric Hebborn, has useful information about drawing materials and practices. This book was written by one of the great art forgers of the twentieth century, who, after being caught in 1984, told his story and revealed his methods. Some of his techniques involve trickery specific to his craft, but Mr. Hebborn also had a great understanding of the working processes of the artists that he copied. His autobiography, Drawn to Trouble is also an extremely interesting read, especially in light of the fact that he was murdered, in Rome, in 1996, shortly after his book was published in Italian. Was it because of something he revealed? A good companion book is The Craft of Old-Master Drawings, by James Watrous.
Historic books focussing specifically on oil painting include A Manual of Oil Painting, by John Collier, 1886; Hawthorne on Painting, by his students, 1930; and The Practice of Oil Painting and Drawing, by Solomon J. Solomon, originally published in 1930.
There has been a proliferation of artist manuals in the past half century. Many delve into very specific techniques, especially on the subject of printmaking. It would be a very long list to write about them all, and I would undoubtedly miss some. There are many great craft books too, but that subject has been written about extensively elsewhere, such as on these two NYPL blog channels: Design by the Book and Hand-Made.
I do think it is important for every artist to be aware of the health risks involved in art-making and the ways to mitigate those risks. For that reason, I also recommend that every artist read at least one of the following two books about the safe handling of art materials: Artist Beware, by Michael McCann, and The Artist’s Complete Health and Safety Guide, by Monona Rossol.