You can import data from another spreadsheet using the importrange() function:

=importrange(spreadsheet-key, range)

spreadsheet-key is part of the url of the spreadsheet that contains the data you want to import. It looks like "0AsaQpHJE_LShdFhSRWZBWWMxem1pZGxhWG1XZzlic0E". range defines the cells you want to import.

In your example, you would look for the spreadsheet-key in the URL of spreadsheet B, and then in spreadsheet A, cell A1, you would put:

=importrange("key-of-spreadsheet-b", "E:E")

Don't forget to surround the key and range with quotation marks.