What are some alternatives?
When comparing SLIM21 and Apollo ILS/LSP, you can also consider the following products
LIBRARIAN - Comment on any arXiv paper
Alma - Meet Alma, a modern and affordable integrated student information system (SIS) and learning...
Eloquent Library - Eloquent Library contains all the functions available in traditional Integrated Library Systems, plus everything required to build and maintain a virtual library.
Sierra ILS - Sierra is designed to make your library effective.
LibraryH3lp - LibraryH3lp provides a flexible, affordable customer service software platform for libraries, educators, and non-profits that combines website chat, texting, email, and knowledge bases.
WorldShare Management Services - WorldShare Management Services is a cloud-based library services platform that saves you time and money by helping you easily manage library resources in all formats.