Hi guys, so I'm running enemy within, running it for my players, and was wondering if anyone has a guide on how much xp the party should have at certain points in the story.

I originally thought it was 1 rank per book, but my party is going through book 1 surprisingly fast. They finished the party and are only at 5xp.

I know its supposed to be 1 per session, but as this is a campaign, and things get harder as they progress, I'd like an idea of the progression they should go through. Thanks.

Eh, things don't really get that much harder as it progresses. I found I had to crank up encounter difficulties significantly throughout book 2, and the listed road encounters were mostly pretty weak. In other words, don't sweat it. The scenario encounters won't result in TPKs (at least not before the climax), so your worst case scenario for zipping ahead is "mild lack of challenge".

The final encounter in book 3 is an exception, but even if your PCs are Epic rank, they probably won't have raised the one and only stat that really matters for that scene. A sizable portion of the party will be overwhelmed by the back-to-back Terror checks, and adjusting XP accumulation is unlikely to really change that (since most PCs will never take a career that even offers Discipline/Willpower). If that worries you, you can reduce the Terror ratings / frequency in the final scene, but since it is the climactic final confrontation it's really not so bad if most of the PCs pass out / die / go mad then.

Alright, well to keep them entertained with new stuff, what would you suggest? Should I try for 10 xp per book or what?

I would just go with whatever rate of progress you usually do. As noted, the final encounter in the Temple is the hardest (barring the post-script chaos realm scenario) and many of us tinker it a bit to not be such a continuous stream of Terror checks.

My PC's wizzed along too not poking around in details very much, they are rank 3 by the end.

About 10 XP per book was also my choice. At the end of the Middenheim excursion my party will have abour 25-26 XP.