hardhat, the frontline staff on the desk will be the library assistants (which ARE admin roles, I totally agree, involving doing the tasks you describe). The librarian role will be the more senior position: their tasks are many and include:
General management of the actual library building and its day-to-day upkeep - arranging contractors/building works/repairs and improvements etc.
Management of the staff including all recruitment and interviews, training, and other personnel issues.
Management of the frontline service on the issue desk including making sure staffing levels are appropriate; managing rotas etc. Dealing with customer complaints.
Management of the resources budget and all the stock ordering. So financial and planning skills come into play. You have to know your resources inside out, keep up to date with new trends and technology. You have to know your users really well to know what they want on their shelves so will be involved in maybe planning customer surveys etc
Management of the IT facilities (again including planning and budgeting, and day-to-day operations), so your IT skills have to be excellent. This includes the public use internet machines as well as the computerised library management system, which you will have to know inside out.
Cataloguing all the books and DVDs etc onto the library management system. so you have to know the Dewey Decimal system inside out and be able to categorise books in a set, standard way, from many different subject areas outside your own specialist knowledge. So your general knowledge has to be excellent too. As far as getting new books ready to go on the shelf the library assistants generally only do basic stuff like the labelling/backing/security tagging of the new books, and then the actual shelving. The end user doens't see everything that has gone into it PRIOR to that point.
Attending local area planning meetings etc.
There are a LOT of skills involved, believe me. A librarian is very different to a library assistant, even though people just tend to call everyone who works in a library a "librarian".