This website (http://www.rarebookroom.org/) has a great collection of high resolution images of rare books covering arts, history and science. For each book there is a viewer with thumbnails that allow you to browse through two page spreads. You can then zoom in to quite a high resolution. The books are phtographed from start to finish so you can appreciate the bindings, frontispiece, diagrams and text and how thay all interrelate.
This is quite a treasure trove. As an example, you can find a complete set of page view images from Robert Hookes splendid book on microscopy, Micrographia, which was published in London 1664.
I have seen some of the images from this book before, but never in their proper context, nor at such high resolution. The images below show the spread of pages 114 and 115. The text on page 115 shows some of his explanation of how he obtained these images of cork cells.The figure on page 114 shows Hookes drawings of longituidinal and transverse sections through cork and where he obtained the sample (Hooke found these small separated structures reminded him of the cells of monks and he used that term to describe them - they have been called cells ever since).