I am not aware of any QlikVeiw administrator specific book, except for the one you get by following our QlikView Server/Publisher training.
I would advise you to ask your employer if you could simply take that training. It is a 3 day training completely focused on installing the server, doing administrator tasks with the server, the licensing model and how you work with that and clustering server. It is offered by Qlik both online and local in many countries and local languages all over the world.
For books you could look here: Books and literature where you could find excellent stuff for developer-topics. Admin releated things are quite rarely only the book Server and Publisher from Stephen Redmond gives a small overview.
But I think if you searched within the community for your questions you will find already many answers and if not you could post a new question. If possible you should do a training like suggested from Onno - it will help a lot to be able to ask the right questions.