The Library of Trinity College Dublin has a free on-line edition of the Book of Kells where you can click through all the pages.* Clicking the up/down keys will enlarge/reduce the image. The Book of Kells contains 340 folios and its illumination is extremely elaborate.
This Gospel book was created around 800 AD, written on vellum at a Columban monastery somewhere in the British Isles. Its name derives from the Abbey of Kells in County Meath, which was its home for much of the medieval period. The leading theory of its origin is that it was started at Iona and evacuated when the Vikings raided the monastery there; after which it was brought to Kells where it was completed. However, there’s no real way to make a decisive ruling on these sorts of questions. Kells was itself raided by the Vikings several times in the tenth century; yet the volume survived we know not how. Missing pages at the front and back may suggest a struggle, but of course many books lose pages without attempted pillaging.
It looks like the book was the work of three scribes, working often from memory rather than from a copy book. The manuscript is written in insular script, mainly in caps with the occasional lower case letter. The book has been rebound several times. An 18th century binding resulted in harsh cropping leaving parts of some of the illumination bleeding off the page. In 1953 the work was bound up in four volumes by bookbinder Roger Powell. Two of these volumes are usually on display at the Trinity College Library.
The Wikipedia entry on The Book of Kells is quite extensive. Most of the above is drawn from there.
*Link via Erik Kwakkel, whose blog, Medieval Books, can be found here. It is full of fascinating stuff.