When he was twenty-five years old, Jean Grolier introduced gilding into Western bookbindery, which is more than you've ever done.
Actually that's probably the wrong way to start; it's unnecessarily hostile, and what is worse, the wrong way round. Let's try again.
Jean Grolier de Servier was born in the area of Lyon, in 1489 or 1490; tradition formerly held the date to be 1476, which is wrong. He was heir-apparent and subsequently lord of the house d'Aguisy; being a vicomte is one of those things that helps when you want to be the prime patron of early 16th century bookbinding. In his early life he mostly made a solid name for himself in finance.
It was when Grolier, who was of an Italian family, was made ambassador to Rome that he began collecting books. He made most of his purchases from the Aldine Press; several of them were printed especially for him, on vellum or on better paper than the normal Aldine runs. He became a friend and benefactor of Aldus Manutius, whose own biography is far too august to even summarize here; suffice it to say, one of his punch cutters invented italics. That's the kind of thing we're dealing with here. (Grolier was in his time a significant mecenate of scholars and intellectuals in general, in fact: we are told by a contemporary that he once, at a banquet he gave for various men of letters, had promised his guests a gift of fine gloves; when, after the dinner, the gloves were set forth, each of them was filled with jangling gold.)
For the proper appurtenance of these books, Grolier employed, in the course of his life, some fifteen bookbinders; in the modernity-age of the now, they and their works are differentiated by the various decorative stamps used to embellish the covers of the books. These stamps being hand-made, the more complex of them are unique, and thus a sort of abiding fingerprint or signature. Some of these men — Jean Picard, Claude de Picques — we know by name. Most we do not, nor in fact by any other works; they are given names by their characteristic stamps, so that one is the Cupid's-Bow Binder, another the Lily Binder, and so on.
Which brings us around handily to the books themselves.
The early Grolier volumes are extremely characteristic, being decorated with large geometric patterns supplemented with amounts of arabesque varying from none to filling out the entire border of the cover and imposing on the central cartouche; the geometric parts are often painted or dyed in, but — here's the important part — all of the pattern lines are gilt. This is a technique which first appeared in Europe on some volumes of the Aldine Press, and which tradition ascribes to the behest of Grolier; the Arabs had been decorating their books thus for centuries, but blind-tooling was the European mode until this point. In any case, the library of Grolier contains the finest works of European gilding from this time, and, judging from the prices the books now command, they hold up well against the best of later eras.
The later volumes typically feature only the arabesque designs, which, incidentally, are normally azured on the Grolier books, more frequently the later they were bound. »Azuring« is a concept borrowed from heraldry — which, remember, was alive and well at the time — where the color blue is represented in monochrome illustrations as a field filled in with diagonal lines. This method of filling a pattern element was for some time fairly characteristic of Grolier; the other modes are full and hollow, which ought to be fairly self-explanatory. (I have here before me a picture of a Grolier volume where the arabesques are hollow and flecked with white or silver spots; I don't know how common that was.)
It is worth noting that while Grolier was at least nominally French, and many of his binders decisively so, the style of his bindings is Italian; however, it could perhaps be said that the later French style of decoration evolved partially out of the style of Grolier, as many of the other significant early French patrons of bookbinders, such as Mahieu, were his acquaintances and patronized the same binders. Notably the later Grolier volumes more closely approach the French style of the time.
The library of Grolier, in the end, consisted of some 3000 volumes, mainly Aldines, all fantastically bound. After his death, the books remained in his family until in 1675, the library was broken up and sold; the volumes are spread now to the four corners of the Earth, and when sold cost the sort of money one is relieved not to have, so that one cannot waste it on a single book. The Grenville bequest to the British Museum supposedly contains six; I don't know whether they are anywhere on display.
He had one more characteristic device, imitated by many bibliophiles since: he had his books stamped with some variant of the device IO. GROLIERII ET AMICORUM, »property of Jean Grolier and his friends«. Worth taking after.