I have suggested that, at least for urban areas with good transport links, fewer but bigger libraries tend to be better. This goes against the grain of many people, who want as many library buildings as possible. It also has not been a policy generally pursued. I suspect because of the sheer controversy associated with consolidating the numbers of libraries, many authorities, such as Lambeth and Islington have gone to great lengths to keep their buildings open.
Let us look at the example of Willesden Library, which has sixty odd PCs. Some of these are drop in, some are bookable, and some have special facilities such as scanners. If you go into a building with that many PCs, the chances are some will be free at any one time. If the same number of PCs were scattered across more than one building, your chances of turning up and finding all the PCs occupied would be greater. Where you are looking at specialist equipment such as accessibility software or scanners the total number in even a big library like Willesden might be quite small. If a smaller library has such facilities at all, there may be only one PC available when you want to use it. In that sense the bigger library becomes inherently more accessible.
A similar logic applies to book stock. The bigger library is more likely to have multiple copies of a given book, so that if demand is enormous (for say text books in the run up to exams), the bigger library is more likely to have them to hand.
This is also true if there are break downs. If say a printer gets broken, the big library with multiple printers can help you get round that. A smaller library with only one would just have to wait for an engineer.
When we were going through our Libraries Transformation Project in 2010/11, it was pointed out to me that Islington was keeping a dozen libraries open in six sets of pairs. Each pair would keep a library open three days a week and the pairs would alternate. That is ingenuous in terms of avoiding building closure, but doesn't make the maximum use of resources since half the PCs and books would be in a closed library half the time.
Another advantage of bigger libraries is that the wider number of activities in a bigger library such as Willesden can draw in a bigger audience, and the sheer size of the building has greater flexibility, so you get more flexibility for different activities. For instance a noisy children's group can take place simultaneously with quiet study on the top floor. That is harder if the space is constricted.