Soft binded thread stitched book (as paper-bound book) is used repeatedly while the quality of its binding is dependent on the strength of the book block. Paperback thread stitching through the folds of the book work (without spine material) is performed on a machine for book stitching. This paper presents the books made of five different types of paper (woodfree uncoated, woodfree calendared paper, woodfree coated, voluminous and recycled paper). Papers of different weights in the range of 80-170 g/m2 have been used. Each book was a 64 pages volume (4 book work of 16 pages), and a total of 60 samples of books were made. In the paper, spines of the book block stitched with thread were reviewed, while changes in size and shape of the holes i.e. openings in the spinal bend of the folded book work through which the thread passes as well as characteristics of the paper surface were observed under the microscope, photographed and analysed using visual assessment. The aim was to investigate whether the selection of paper type and weight significantly affects the strength of the book block when the bookbinding processes of folding, collating and sewing are standardized. It was shown that the woodfree uncoated paper and calendered paper were the better choice for paper-bound book binding in comparison with the voluminous, recycled and woodfree coated paper in which significant changes in size and shape of the holes were observed.