How to recover data from MacBook which won't startup properly?
If you happen to have a thunderbolt cable and a spare mac you can try your luck with target disk mode. Target Disk Mode is a feature that allows a Mac to act as an external hard drive. 


Connect the two computers with a FireWire or Thunderbolt cable.
Start up the computer to be used as a disk in target disk mode:    


If the computer is off, start it up while holding down the T key. 
If the computer is on, choose Apple menu > System Preferences, click Startup Disk, and then click Target Disk Mode.


When the computer has started up, a disk icon appears on the desktop of the other computer.
Transfer files by dragging them to and from the disk. 
Eject the disk by dragging its icon to the Trash. While you drag, the Trash icon changes to an Eject icon.
On the computer you used as a disk, push the power button to shut it down, and then disconnect the cable.


Instructions thankfully provided by Apple's KB