This is a very handy tool if you're reviewing basic Latvian or if you already have a background in highly inflected languages and/or linguistics. Personally this app has been very helpful for me in brushing up on Latvian. I'm an American heritage speaker of Latvian, but I get very little practice, so this is great for me. However this app does little to explain the grammar or why/how noun and verb endings change the way they do, so if you don't already have a firm grasp on the concept of noun declension (nominative, genitive, dative, etc.), you will have difficulty understanding how to use the wealth of vocabulary this app presents you with. Overall, I give it four stars for comprehensiveness of basic vocabulary and sentence structure. It would have been five stars if there were more grammar resources, such as declension and conjugation charts, explanation of when to use nominative (subject) nouns versus accusative (object) nouns, etc.
Also if you are using this app on an iPhone, you will need to enable a Latvian keyboard to use certain special characters.