As TFIN50 and TFIN52 cover important topics you can start your preparation with these but you will need other books as well. You may pass the exam without the other books but you may not get good percentage. Besides exam, I believe that it is good to have better understanding on Solution Manager (SM001) and Business Processes in Financial Accounting (TERP01 and TERP21). These two topics are not covered in TFIN50 and TFIN52. Solution Manager (SOLMAN) is a standard platform for Application Lifecycle Management. It provides tools to monitor and streamline the process. Because of its uses most of the SAP customers have already implemented or either planning to implement Solution Manager. So by making your basics strong in all the topics will not only help you excel in the exam it will also give you confidence to perform well in the current competitive world.
All the best!
Priya