A series of phonics books by Shree Publishers focuses on word sounds and sight words. There are about 12 books that focus on various vowel and consonant individual and join sounds like ch, oa, u, e, a, i etc.
By sheer repetition, like most early reader books do, it makes the child start reading fluently in a few sessions.
The words are coloured differently and the index lists out whether they are sight words or phonics focus words.
I normally indicate to the kids what we are focusing on and make them aware of the join sounds before reading the book.