The "Download Now" link directs you to the iTunes App Store, where you must continue the download process. You must have iTunes installed in order to open the link, and you must have an active iTunes account to download the application. This download may not be available in some countries.
From LoL Software:
Knots, Splices and Rope Work is the complete original 1917 classic treatise by A. Hyatt Verrill, the renowned American inventor, author, illustrator, archaeologist, explorer, zoologist and friend of former President Theodore Roosevelt. (If you know of anything else Hyatt was involved in please let us know :-) This App will appeal to outdoor enthusiasts, scouts, sailors, rockclimbers, bushwalkers, fishermen and anyone interested in exploring the uses and history of knots. This App includes scrollable text of descriptions and 154 diagrams of classic knots, splices and rope work to help you learn and practice the art of knot making. If you are planning to circumnavigate the world solo in a yacht, we strongly recommend you buy this App as part of your preparation. If not, you might still enjoy it.