2) 'Like Clockwork' (26.4 MB) $5.0

A Review in 'New Scientist' (13th January 2001 No2273) said this "Like Clockwork does for photosynthesis what A Brief History of Time does for theoretical physics: it takes a baffling but fundamental process and makes it easy to understand. David Alan Walker uses the electronic book format to explain the transfer of energy from sunlight with lots of clear, colourful diagrams and relevant links."

N.B. At 26.4 MB for 129 pages this may seem extraordinarily large but this is because its hyperlinks offer a little animation and music. It is a book which was written expressly for the computer screen.