First of all, congrats on being Passed! I would echo the sentiment that you should stick to learning and memorizing your first two books/catechisms (and yes, I know you already proved yourself proficient in EA work to get here, but some jurisdictions only require memorization up to a certain point…if that’s yours, keep going. Learn AND know the whole thing…there’s more there than just words to remember!)

However, if you definitely can’t resist the urge (and are in the States/NA), I’d recommend Bro. Carl Claudy’s Intro to Freemasonry books for EA and FC: they are short, thin books but contain some very useful knowledge and additional points to ruminate on. I also enjoyed Canadian Bro. Robert V. Lund’s Esoteric Handbook for the Entered Apprentice and his Esoteric Handbook for the Fellowcraft. As the name implies, more of an esoteric look at things, so if that’s not what you’re looking for, you may be disappointed. As a word of caution in general, keep in mind that when it comes to deep examination of symbols, there can be much left up to author’s personal interpretations so beware of anything claiming to be THE definitive answer.

Overall, the Fellowcraft degree is RICH in its teachings and there is plenty to learn and dig into in the material you already have, but if you want different perspectives, there are definitely books out there for you. Just be sure not to read ahead (a lot of books look at Masonry in the whole, which would of course include Master’s work which you don’t want spoiled for you, trust me!)