This is the second version of the wizarding world's Knight Bus. There are many similarities between the two versions in that they are both double-decker purple buses. The main differences between the two is what's included with the buses.
The first edition came with a bush, lamp post, trunk, owl (Hedwig), dog (Sirius Black), Harry Potter, and Stan Shunpike. The second edition includes a trunk, owl (Hedwig), Harry Potter, Stan Shunpike, and Ernie Prang. The both also have the shrunken head, but the head in the first version is a sticker on the windshield, while the head in this version is a round LEGO® brick with the head's face on it.
As to the buses themselves, the main differences there are in the back of each bus. The back of the first bus on the first story is enclosed, just like the rest of the bus. But on this bus the back on the first story is partially open with a pole. This allows Harry to enter the bus from the back if he wants, or he can ride the bus while holding on to the pole. Given how Ernie likes to drive, though, this may not be the safest way to ride the bus!
Set 4866 - The Knight Bus (2nd Edition)
Year Released: 2011
Set Number: 4866-1
Name of Set: The Knight Bus (2nd Edition)
Book Set is Based On: Harry Potter and the Prisoner of Azkaban
Number of Parts: 268
Minifigures: 3 - Ernie Prang, Harry Potter, and Stan Shunpike
Creatures: 1 - Owl
Minimum Recommended Age to Build This Set: 7 years old
More Pictures of This Set
Image Source: All images are from my collection
This LEGO® set contains small pieces that could be a choke hazard and is not meant for children age three and younger. LEGO® is a trademark of the LEGO Group of companies which does not sponsor, authorize or endorse this site.