They are very different books, Mythic Locations (ML?) is essentially a 'scenario' book, providing locations that can be used directly in stories, while Between Sand and Sea (BSaS?) is more like a tribunal book, but for an area not claimed by the OoH - somewhat similar to tC&tC in that way.
I want all three, as all three can be nice to add to my campaign. I just dont know which one I want to buy first.
Hooks I can use this books with some alterations to fit in with my campaign where the players live on the island of Samos, when I am out of ideas.
Between sand and the Sea The group's gifted Mecere is starting to get an interest in the Ring of Fire and just finished her Redcap Duty as a spy in Trisoxiana to gether info about the Mongols, in which I used the other players as a Sahir, a djinn and a Arabian Prince. So if this book is as good as TC&TC It will be a welcome addition to the travels in the group's travels along the southern shors of the med.
Mythic Locations With some altaerations, I might be able to use most if not all of these stories in greece and the surrounding areas.
From what you said, I think you'll get most use out of BSaS, since it's basically a MUST for anybody interested in The Ring of Fire. But I do highly recommend Mythic Locations, as it's a GREAT book. Mostly all locations can be moved to the Theban Tribunal (I'd know, I'm doing exactly that myself), and one of them is even actually set in the Sea of Marmara! But all three are excelent books, and Hooks is a great source of little short stories, very easy to quickly deploy anywhere without almost any work whatsoever.
Bear Island. I was playing in/running a Thebes Tribunal campaign at the time I wrote it. It is one of my favorite bits from the Argonautica so I ported it into the saga for my players. They didn't end up building their covenant on the island, but certainly enjoyed fighting the . . . well, I don't want to spoil the fun.
I was really happy when I saw Bear Island in Mythic Locations, Matt. I'm currently setting up things for my group to visit the place, but it's so fraught with wonderful stuff that I don't want to make it just a quick tourist visit, so I'm building up to the visit so that it can become a recurrent place to visit. Thanks for writing it!
While I agree that BSaS is probably the way to go based on what's already been said, I have to chime in that Hooks has at least one story dealing with Automata/Mechanica. And considering the saga takes place in the Theban Tribunal, that story might be worth the price of admission alone. After, of course, BSaS.
I'll try to answer witout bias. All three books are excellent in their own right. Good to hear you intend to get them all.
Hooks isn't specific to geography, most of it can be used anywhere. But it is really only good if you want to introduce another book, and the themes and activities this particular book emphasizes. If you know in advance that your troupe is not very interested in micro-managing lab Upkeep and supplies, nor in dealing with mundane trade and income - then don't run "A New Deal". Because then City & Guild most likely isn't a very interesting book for you.
Mythic Locations is specific to geography, but much of it can be shifted around to also fit in Thebes. The excellent location Bear island is right in your backyard though. I ran this for a group, and there is much potential and material here. It was a particularly slow-moving troupe, and they spent a lot of time on a small thing ,which was almost just a foot note, and never really got to the bigger things. Is this a new or an ongoing saga? Many of the locations can be used as kick-off to a saga starting up and remain a focal point, but can as easily be used as a long-running plotline. Or a location can be pulled out of the hat in the absence of any other plots for a group of magi with no running projects. With little extra work for the SG.
Between Sand and Sea is a world book, and for an area close but not really that close to Thenes, when comparing to Cradle and Cresent. Still, if the saga is outgoing and someone fancies exotic locales, strange new cultures and daring expeditions it's a good bet. The book has lots of material to develop stories and plots yourself. But not as quick to use as in 'Locations above.
So I feel Hooks is good for smaller things, while the other two for larger storylines.