Reddit reviews Airframe Stress Analysis and Sizing

Bruhn, Niu, Roark and Niu (again) are the bibles for aerospace structures. Bruhn is always ridiculously expensive but it's hard to beat. Not sure why they won't put another edition out, everyone uses it.

Best way to learn FEA is by doing. Taking a class to understand the theory is very helpful (in my opinion). Gives the user a deeper insight into how the model is working - especially how the nodal DOFs of each type element work. Making models in "one button push" FE packages like Solidworks or ProMechanica is only so helpful. Building the models by hand or creating your own programs is the best way to develop an understanding.

If you are motivated, here is a good class with all the chapters and notes online.