Yes..K and B is enough...For threads as well as API..Atleast i got everything from K and B...Any material cant help you completely on threads because the questions are more logical than technical...You can easily understand the code but it may be difficult to understand the flow...One way you can help your cause is to answer more and more mock tests...But you need to be carefull that you are not carried away too much in Thread world because only 2-3 questions on thread will be difficult and not all...