The arrangement of Samuel Pepys's library was a matter of great concern to him, from the commissioning of the special glazed book presses in which it is still housed to the positioning of volumes by size, with blocks cut to make the volumes level. In the early 1690s he arranged for a catalogue to be compiled. This consists of the usual listing in order of shelf-mark to be found in earlier library catalogues, but in addition there is one of the first attempts at a comprehensive subject-index, an `Alphabet' of the books, their authors and topics. This is of the greatest interest to historians of libraries and of intellectual attitudes in the late seventeenth century; it can be seen as an extension of the ideas for classification in the sciences discussed at the Royal Society (of which Pepys was President). Furthermore, additions and emendations made up to Pepys's death in 1703 shed light on Pepys's collecting practices and on a major reshelving of the library carried out in that period.