Speaking of the UN...

While not solely on the UN, a book I highly recommend is entitled "Lords of Poverty: the Power, Prestige, and Corruption of the International Aid Business." It is the most damning book on the international aid BUSINESS I've ever read. While almost 2 decades old, it is still relevant in its criticisms. It makes a great companion read to Easterly's "The White Man's Burden," but from a more journalistic and less economics oriented viewpoint. The issue is that when the idealism of the goal (whether peacekeeping, aid, assistance, development, etc.) eliminates any possible manner of questioning the viability of the method. That is the difficulty of almost all international organizations supported by the largess of the world's taxpayers. The countries paying the bills cannot even slow the constant increase of (and cannot even contemplate the possibility of lowering or eliminating) their support for wasteful and even dangerous UN organizations without being attacked as heartless. A relatively high level of inefficiency in a large scale organizations with varied goals, allegiances and priorities is understandable. The current system is run on patronage and the idea that 'moving money' is the goal, not helping people efficiently. Managers in many of the institutions are rewarded on the basis of dollars loaned and therefore. There is no outside organization capable of accurately examining the practices of these organizations and even when the internal 'auditors' of such groups manage to create an unbiased report about their failures the information is either suppressed or ignored.
The only criticism I have of the book (besides the fact that it is incredibly depressing) is that, while Hancock is excellent at pointing out problems, he limits his solutions to 'starving the beast.' From reading his book you know that the built in power structures and patronage of the 'system' will make that practically impossible. Easterly's options of gradually reforming and refocusing is more feasible.