Assessing the impact of scholarly books is a difficult research evaluation problem. Library Catalog Analysis facilitates the quantitative study, at different levels, of the impact and diffusion of academic books based on data about their availability in libraries. The WorldCat global catalog collates data on library holdings, offering a range of tools including the novel WorldCat Identities. This is based on author profiles and provides indicators relating to the availability of their books in library catalogs. Here, we investigate this new tool to identify its strengths and weaknesses based on a sample of Bibliometrics and Scientometrics authors. We review the problems that this entails and compare Library Catalog Analysis indicators with Google Scholar and Web of Science citations. The results show that WorldCat Identities can be a useful tool for book impact assessment but the value of its data is undermined by the provision of massive collections of ebooks to academic libraries.