I disagree. You will struggle to pass if all you read are those two. I recommend that my students do buy and learn from one of the PPL sets - the AFE ones seem the easiest to use for most people.
And you really shouldn't go into learning the theory with the attitude "I just want to learn enough to pass the exams, then I can forget it." To be a good pilot and to get the maximum enjoyment from your flying, having a good knowledge of the subjects is needed - you will actually use most of it.