I have been working on two German theologians - Albert Schweitzer and Ernst Käsemann. Although, I would not recommend their writings for a young Christian (at all!), they do have lots of profound insights into Paul in particular. Interestingly, they have polar opposite views on one question - the current location of Jesus:
Käsemann: ‘Paul knows no invisible Christ whom one can localize only in heaven’
Schweitzer: ‘For Paul, as for all the believers of his generation, Christ is in Heaven, with God, and nowhere else’
Who do you think gets it right?!