Medicare needs fixing. The program has its strengths; it is popular among beneficiaries, has very low administrative costs (maybe too low), and, since its inception, has greatly reduced financial risk exposure among beneficiaries. Nevertheless, it is unaffordable and inefficient. Jeanne Lambrew and Henry Aaron take up both of these challenges for Medicare reform in great detail in Reforming Medicare.
Horwitz, Jill R. Review of Reforming Medicare: Options, Tradeoffs, and Opportunities, by H.Aaron and J.Lambrew, co-authors. J. Econ. Literature 47, no. 3 (2009): 834-6.