Best book to study literary theory and literary criticism? Beginning Theory by Peter Barry!

Yes, today I am deviating from my path just a little to accommodate a very important question that many of my friends who are the students of English literature eight have in their minds. I have been through this phase as well. As soon as literary theory jumps into the scene, the otherwise easy study of literature becomes a little tough and students, who are the beginners, begin facing problems. The problems mainly occur because they don't know about any book that can help them understand literary theory from the beginning or the basics. Moreover, by mistake, if you purchase any advanced books like that by Patricia Waugh or Raman Selden, you are likely to be perplexed even more.