Assuming you've mastered undergrad level text like Atkins, you'll want a good textbook on Spectroscopy and one on molecular photophysics. I recommend Bernath, Spectra of Atoms and Molecules, and Turro, Molecular Photochemistry. If you're interested in fluorescence, Lackowicz is classic.
Spectroscopic principles are no different in fs time domain. That's just a matter of optics for generating short pulses.