This book sounds familiar...?

So here I am, merrily tapping away, writing a new book.  It's going well.  It's the first project to break 20k words in a couple of years.

In a completely unrelated occurrence, a book arrives in the post for me.  I can't remember ordering it, although I must have because it...well...arrived in the post.  For me.  This isn't uncommon (not things arriving in the post, but me preordering books and then forgetting about them.  It's like Christmas every so often when unexpected presents appear).

As soon as I read the blurb to remind myself of what it is I've ordered, I have a weird moment of weird.
This book sounds familiar.
So I start to read it.  Quickly.  Without enjoying it.  I read it within a day just to get through it.
Yep.  
Yep.
Okay.
Yeah...this is my book.  And I don't mean, this copy in my hand is my book.  This book is telling the story I've been working so hard on.
Oh, crap.

Okay, let's break this down.  So I ordered a book and then forgot about it, only to crack on with a writing project that, oddly enough, is incredibly similar to this very real, very published novel that I am holding in my hands.
I know what you're thinking.
I started this project after ordering this book.  I forget having read a plot line from the blurb, and then end up taking it as my own and created my own book from it.
Sorry, but there are two flaws to this supposition:
1) The blurb isn't that informative.  It's informative enough to give me the sinking feeling that it may be a little similar to my own work, but not enough for me to create an entire story from it (if you see what I mean).
2) I started my project before I preordered this book (I checked my Amazon order history).
(Perhaps I should have started with point 2...)

The funny thing is that the story is about quantum mechanics and the Many-Worlds interpretation of a number of leading theories, specifically Schrodinger's equations.  It's entirely made funnier because of this fact.  With the possibility of a new, tangential universe being created with every observation made by every possible observer then, of course, there is a universe in which two people end up writing the same story.  Anyway, moving on from this, I'm thinking practically about it.
It's not unreasonable to say that this type of Sci-Fi is very in at the moment, so it's not surprising that I've come across a piece of work that is akin to mine.  Except, the applied science used in this book (I refuse to name it - I refuse to!) is pretty much my own.  So not only have we written on the same topic, but we have taken it to the same level in terms of deriving technology from it that would, essentially, allow the protagonists to access other alternate worlds.  That's weird.  After that, of course the stories are going to be similar as the same ethical and philosophical ponderings are bound to come up.
So, yeah.
Weird.

Surprisingly, it hasn't stopped me from pushing on.  I decided, once I finished the book, that I could do better.  And I would do better.
The science isn't in depth enough.  I'm aiming for hard sci-fi, the stuff that makes your head hurt on the first reading.  I'm working my buns off trying to wrap my own head around elements of science that I never thought I'd ever want to get to grips with and I'm not going to let that go to waste.  
The published story is, at its heart, not about the science either.  It's a love story.  And that's okay, it works, it makes it more mainstream (and I really don't mean that as an insult!) but I'm not looking to take away from the central themes of identity and probability and all that good stuff in mine, so I'm not diluting mine down.  Even if that makes it less marketable.  I'm writing this for me, I suppose.

I hope this means something to others out there who have found themselves in a similar boat.  I know your pain.  And it takes a lot to just accept the reality that someone else out there, effectively, beat you to it.  Of course, I wish the book didn't exist, but it does, however I'm going to outdo it.  That's my resolution.

(If you want to know which book it is, let me know.  It's a pretty good read, if you aren't rushing it...)