When comparing book printing services, there are several important factors to consider, including the quality of materials and finishes, customization options, price and turnaround time, the printing technology used, the level of customer service and support provided, and the company's reputation and reviews. Additionally, it may be important to consider any special requirements for your project, such as specific binding or paper options. By considering these factors, you can select a printing service that meets your needs and ensures that your book is printed to the highest level of quality and professionalism.