Once loose sheets have been collated, folded, gathered together in their sections and then sewn in the correct order they are referred to as a book block ~ book-block ~ bookblock ~ all of which are suitably self-descriptive titles.
A book block usually needs to be trimmed on three sides and covered by some method. Bookbinders, using the techniques leading to fine binding, will usually prepare their own book blocks, so that they have control and experience of the materials. Bookcrafters are avoiding the skills and time required for sewing. It can take a day to sew a large book by hand. A machine can do it in less than a minute.
A bundle of papers glued together (rather than sewn) will also make a satisfactory finished book. Such a bundle also qualifies as a book block, and is important for crafters or binders. They employ that method chiefly for pre-printed materials, such as theses or home-printed books where folio-production is not easy. The term Perfect Binding applies to that type of work. It is quick and easy and economical, and very effective (exemplified by Paperback books).