If lost or destroyed, a new copy can be obtained from the table in Ashdale or from the bookcase in your Player-Owned House made through Construction.
Below is the text you can read from within the book.
Having completed my initial sketches, today I began my inspection of the site. Once complete, the house will stand on a large seastack at the south-western end of the island, offering an excellent prospect of the surrounding area. Furthermore, the stack itself boasts a most remarkable feature: a steep vertical tunnel that leads directly into a large network of underground caves. Having explored only a small portion of these caves, I cannot be certain of their exact size, but it appears they extend for some distance beneath the island. I may even choose to incorporate an entrance to the caves into the house, as there is an opening in the first chamber that leads directly to the sea, and one never knows how such a thing may prove useful.