IT MUST be unsettling, and frustrating, to head to the library so you can check job listings online, or be in a safe place after school, only to find it closed.

According to a report in yesterday's Daily News, unscheduled closings due to staff shortages are happening more often, as the library system struggles to operate under reduced circumstances. On any given day, according to the report, one or more of the 54 branches in the system have been shut unexpectedly.

This is disruptive to the city's citizens; the library is often the heart of a community, providing far more than books. The outcry over Mayor Nutter's original plan to permanently close 11 branches at the beginning of the city's budget crisis last fall were testaments to the library's community role.

The nature of the closings - they shift day by day and are posted on the library's Web site each morning - suggests that those suffering real disruption are the people who staff and manage the system. These "rolling closures" require some staff be sent to different branches each day in order to keep them open. It's hard to imagine the logistical nightmares of managing a 54-branch system when you have to choose each day which ones to keep open.

One contributing factor is that 11 library security guards were transferred to other city departments last year, and the city is still in the process of hiring replacements.

But make no mistake: the real problem is money. The city trimmed the library budget by $8 million (20 percent), and the state cut its public-library subsidy another 20 percent, a $2 million decrease. These cuts have eliminated 115 jobs.

These changes may surprise some, who may have assumed that the outcry over branch-closing plans somehow "saved" the system. But the library is the canary in the coal mine of a troubled economy - and of our denial about the true impact of the budget crisis.

Nutter said his original plan of branch cutting had been based on data suggesting that cuts would "right-size" the system to align with the city's population. He also said it was an chance to rethink some functions, by combining related services. Michael DiBerardinis, who oversees Parks, Recreation and the libraries, is now studying such ways. The libraries, though, should be a harbinger of changes the city as a whole needs to take to reflect 21st-century realities. It's not going to be pretty. But it must be done. *