The reason for the two titles is that this is a two-game package for the price of one. This suggests to me that the adventure market must be fading a little for that is what these two games are.
They are text only adventures with a reasonable number of locations and a full vocabulary is given for both. Whilst they aren't simple, I don't think that they will tax an experienced player.
They are not clones of each other and as the screen style is different I suspect that they have different authors.
Xanadu Cottage's text is in block capitals and there is a shortened version of each description for second visits. It is very simple to restart this adventure as there is no data file to load.
Ebony Tower does have a data file to load and this is a pain because it has to be loaded every time you are killed!
Overall, this is certainly good value for money and there is plenty to keep the player interested. I haven't found the location where you 'undress' yet though!