Existing books that deal with similar content or are of the same length are great places to find inspiration. Chop down other books or large magazines if you don’t find existing books. Think creatively and openly, but realistically. Bring in any comparables to look at next week.
In addition to comparables, create your own book model to communicate the exact size (or proportion) that you feel you’re going for. Your book models may use blank paper or they may include scrap paper or printouts from the recycle bin. If you’re interested in printing in signatures (as most commercial books are printed), you may not need to fold and sew for this week. Glue binding the block is sufficient for now. Note, the purpose of creating a book model is to communicate your idea of how the book should feel. If paper weight or color is important, then track down what you’re looking for now.
Note there are digital printing options at standard sizes and these may prove themselves a good option, but let’s see where your research and interests lead us first.