These Broken Stars by Amie Kaufman and Meagan Spooner
This book is spectacular. It reminds me of what I liked about Shadowfell and Raven Flight by Juliet Marillier--I just like survival in YA. Trekking across dangerous terrain, unsure of your safety and survival. Its just excellent. I loved the whole "going mad" part too. Her distress at possibly losing it was palpable.
The only part I didn't like too much was the part where they first landed on the planet. It seemed as though Lilac was a little more bitchy at this point than she really needed to be to get stubbornness and fear across to the reader, and I don't know, Tarver's reaction to it seemed very much exaggerated in light of their personalities later in the book. But perhaps they can be forgiven under the circumstances, but I still feel like that part didn't fit. I don't know what it is about it, but it just didn't fit with the flow of the rest of the story.
Let's talk about that crash--what a crash. I loved the scene of it crashing, and I loved the scene of the two of them watching it fall to the planet. Her expertise with electrics was refreshing to read. I thought the romance was well done, and not too rushed. There isn't insta-love here, which is always a gem in YA.
In conclusion, if you enjoy survival stories like I do, you will enjoy this one.