But I'm really not sure whether they're good together. A strange thing. Maybe that helps the theme of dualism above all else that's here.
The first game is pleasantly concrete but lacking somewhat in mechanics. Explore a French village, grab items as they appear, keep most of them and use one or two in one or two nicely designed puzzles, then use a large number of them in the right order when prompted. Your end goal is, effectively, (Spoiler - click to show)to obtain a key and transport it to open the endgame area, after acquiring a collection of items needed for the endgame. This is all nice clean fun.
The second game is the gradual investigation and discovery of the secrets of Saunière and the town, and this is executed more clumsily, but still satisfying. It is not quite like assembling a jigsaw puzzle from gradually discovered pieces, or like drawing connections between information- for the most part, it's more like discovering a pile of puzzle pieces first and then slowly uncovering a dozen different ways to fit them together. Into the same picture, at times. After a certain point the novelty of discovery wears off and there's only so many ways the same information can be presented.
That sounds very strange without spoilers, so- (Spoiler - click to show)By the first few discoveries, the player will likely know that the Cathars are involved, that Saunière found some sort of secret, and that there's a hidden meaning in the landscape of the town and its environs. And then in many other ways, these themes will be reinforced without much elaboration. Showing materials to the bookseller will offer somewhat more elaboration but it doesn't feel qualitatively new.
If it weren't for the fact that the player is arbitrarily prevented from doing so, they could stumble into the endgame sequence after almost zero investigation of the town and the tower. And their experience would be worse for it- but not that much worse.
(Spoiler - click to show)Because that endgame culminates in an uninspired 'monster hiding in the cave' ending that bears no particular relationship to any of the mysteries the player has been uncovering so far. And that's the thing that cleaves the two games in twain for me and most severely hurts the experience here. On the technical level, nothing here ruins the feel or becomes distracting. There's a few fiddly aspects to the manipulation of certain objects but nothing out of the ordinary. All in all - I still recommend giving this a play. It's relatively short, and I may be getting too pedantic about criticizing the implementation of the story.