I bought it with my rulebook and I must say I wasn't disappointed. I also bought pdfs, can't wait to play that black dossier!
As for morbid adventures, if you only use rulebook it gives you much new, but not so if you use Shocking tales expansions as well.
Inside you get some necronomicon spells (I haven't had a chance to use them yet, but they look kind of cool). Spells are really powerful, but every time your agents use those spells, they get marked. Marks lead to crazy minds, but thankfully you can erase them!
You get all the scenarios in one book, which also have variants. For example, bag man reversed, a "fight" scenario with only close combat weapons allowed and such.
There are loads of extra quest scenarios, which is really a nice addition. I think I could say I recommend book just for the scenarios, but I can understand the book isn't on the cheapest side.
There are "all" lurkers listed in the book. In brackets as I was really looking forward to kick some dinosauric behinds, but those aren't included. Later I found out, its because they're black dossier's specials (which makes sense). The extensive lurkers list is also a good thing to have.
Keep in mind MA doesn't give you the profiles of the extra agents that you can get in the pdfs.
There is also a short paragraph about playing multiplayer and solo games. Didn't get a chance to try multi, as I didnt yet got an opportunity to show the game to "wider public", but don't expect too much from solo gaming rules. The paragraph on solo gaming was honestly biggest drawback for me.
In the end, you also get a combined weapons chart which greatly expands available arsenal.
When I play, I got both books open, but as it was said before, you use MA way more. If you tried the game and you like it, I am sure you won't be disappointed in MA. There is so many available lurkers, its sometimes hard to make a choice!