Is there any book where specific heat capacities are given?
There are several databases of thermochemical properties, a number of them being listed on this Wikipedia page (at the bottom). Most of them are not freely available online, but require subscription. I've searched online but couldn't find that information freely available.

Another possible way to get the information would be through a search of the published literature (scientific papers). You can, for example, find this information on magnesium nitrate in a 1944 paper in J. Am. Chem. Soc.. However, I had no such luck with Al(NO3)3 · 9 H2O .



Clarification: the answer above is for the crystalline compound aluminium nitrate nonahydrate, which as @Ivan stated, may not be what you actually need for your calculation if the reaction is in water.