Those images are kind of small - the titles are The Blood Diamond Treasure and The Mystery of the Broken Cross. The main character in this series is a 14yo girl named Lydia Barnes:
Lydia Barnes is not your typical 14-year-old. Sure, she plays her iPod nonstop and rolls her eyes at her dad's dumb jokes - but she also finds herself dodging lion attacks, outwitting rebel warriors, and heading up globe-trotting adventures.
In The Blood Diamond Treasure, Lydia is on a trip to Liberia with her father and her tutor, and gets involved in a treasure hunt with a new friend. In The Mystery of the Broken Cross, she and her father are in Israel, when she finds herself accused of stealing money from a Christian relief agency and must try to find out the truth before terrorists strike. In each of Lydia's adventures, she (and the readers) learn what life is like in other parts of the world, and about God's love transforming others.
I bought these first two books in the series, thinking that possibly my kids would like them, and a second set thinking that they might make a good gift for my niece and nephew. (I will actually be putting those in the mail this week, as my niece's birthday is coming up quickly!) Once I got them home, I was a little concerned because the lead character is a GIRL and I have BOYS. (well, I have a girl too, but this is a little beyond her reading capability at this point!) However, I gave the copies to Spencer and Landon to keep in their room and waited to see what would happen. I waited until last week, and really hadn't thought too much more about it. One night I had to remind them to turn out the light and "go to sleep already!!!" and Landon stalled with the classic statement (and as a lifelong bookaholic, I was immediately sympathetic to his plight!) "but I'm almost at the end of the chapter!!" I asked what he was reading and it was Lydia Barnes. 
Landon has really enjoyed these first two books in the series, so we are anxiously awaiting the coming installments. The forward in the book indicates that we can expect Lydia to travel to Jamaica next. There is also a website: LydiaBarnes.com - which we have yet to visit, but where the book tells me we can read Lydia's blog, play games, and find ways to help those around the world.
I read the book in a couple of evenings, and was really impressed by it - the characters held my interest right from the start, much of it was reminiscent of POTC except that there was a definite undercurrent of a Christian rather than mythic theme. It wasn't until I'd finished reading and started recommending it to some like-minded pirate fans that I noticed that it was categorized as "youth fantasy fiction" 
- well that explains the short chapters, I guess. LOL But other than that, I didn't notice that it was particularly "young" and since I am a 40ish mom of four, I think that says something about the broader appeal of this particular book. Oh, and it's beautiful - I mentioned the striking cover art, but each page of the book also adds to the visual appeal - printed in sepia-type tones, rather than black on white, each page looks a little like a page from an aged manuscript. Easy on the eyes though. My understanding is that this is the first of a planned trilogy - I, for one, am anxiously awaiting the next instalment!