Starting with Unicode 6.0, the standard is no longer published as a book. It can be downloaded from the Unicode website, but 2,775 pages is quite a mouthful for a trusty office laser printer.
A more attractive option is to have it printed by a print-on-demand publisher such as Lulu. This page provides the tools and cover art needed to prepare a 5-volume version:
Volume 1 contains the specification text itself, including appendices, references and index.
Note: This volume has unnecessarily wide inner margins and an extraneous copyright line added to the bottom of each page. The text could be made a bit bigger by removing the copyright and scaling the page accordingly.
Volume 2 contains all the character charts except the ones for Chinese characters (Chinese/Japanese/Korean/Vietnamese ideographs), which are split between volumes 3 and 4 as detailed below.
Volume 3 contains the Chinese characters from the Basic Multilingual Plane (plane 0), viz,
Volume 4 contains the Chinese characters from the Supplementary Ideographic Plane (plane 2), viz,
Volume 5 contains a complete radical–stroke index covering all the Chinese characters in Unicode.
The downloadable archive contains LaTeX files for generating the interior of the books from files available on the Unicode site, a Makefile for Mac and Unix that can be used to obtain the files and run LaTeX automatically, and custom-made cover art for each volume featuring a pattern made from U+FFFD symbols.
The size of the finished books is called Crown Quarto, which is a bit smaller than US Letter (the format of the original files), but has exactly the same proportions.
Paperback copies can be ordered from Lulu in the UK for around £10 sterling for each of the 650-page volumes (similar prices in other countries).