The Enemy in Shadows indeed is a faithful and improved remake of the original first modules of the Enemy Within campaign. The thing is that the source material just didn't age that well.
At the time of the original release, this campaign was groundbreaking. It was first to move away from "kill 'em and take their stuff" adventures, focussing instead on memorable NPCs, involved plots and putting investigation ahead of fighting to solve problems. So at the time of it's original release this would have gotten a 5-start review from me.
BUT: Looking at the adventure (new and old versions alike) from today's perspective, one can only note that this is a tight railroad. This doesn't have to be bad, as railroading sometimes is needed to tell a comprehensive story. But this railroad has some very bad "derailment points", of which I just mention a few below:
a) The whole plot hinges on on PC being a look-alike of a deceased (evil) NPC. But what happens if this PC dies? This is a real risk in a game as prone to random death as Warhammer. So you either give this one PC strong Plot-Armor or you can scrap significant parts of this adventure (and the next modules as well) if the PC passes away
b) Some logic PC action is completely ruled out and disregarded: The secret temple in the sewers will be cleaned out, no matter what the players do (i.e. put one PC on permanent guard there); the secret door can't be found no matter what; the cult traitor can't be protected no matter what; the players will be framed for murder no matter what ...
c) The investigation in Bögenhaven doesn't advance by smart thinking of the players. It is a thin trail of breadcrumps of NPC accidently dropping secret letters and notes out of their pockets. Nicely signed with a heptagram and a the skull of some beast
d) The final reveal comes with one big cultist getting cold feed and spilling the beans to the PC. But this only works if the PCs have contacted/questioned him before. But there is very little reason for the PCs to do that. So the whole plot breaks down if the PCs don't contact this one person out of the blue.
e) The opening adventure of the the next module Death on the Reik assumes that the PCs "befriended" a healer/herbalist in Enemy in Shadows. But there is no hook why they should befriend her. She is one of many tradespeople selling their products at the Schattenfest fair ground. PCs MIGHT talk to her, if they need healing herbs, but they for sure will not befriend her.
For above reasons I would give the source material a 1/5 stars from today's point of view. The good production quality of the new version raises it to 2/5 stars. Shame that they didn't decide to fix the weak points of the original though.
(Note: I GMed both the original verision some 30 years ago as well as the current version just last month. We decided to not continue the campaign for above mentioned reasons)