SQL Server 2012 :: Behavior Of Brackets In Select Clause When Declaring Variables?

I can't understand why I get 2 different results on running with a Bracket I get 'NULL' and without a bracket I get the declared variable value which is 'Noname'

Below is Query 1:

Declare @testvar char(20)
Set @testvar = 'noname'
Select @testvar= pub_name
FROM publishers
WHERE pub_id= '999'
Select @testvar

Out put of this query is 'Noname'

BUT when I type the same query in the following manner I get Null-------Please note that the only difference between this query below is I used brackets and Select in the Select@testvar statement

Declare @testvar char(20)
Set @testvar = 'noname'
Select @testvar=(Select pub_name
FROM publishers
WHERE pub_id= '999')
Select @testvar