Say It in Sinhala,⭐⭐⭐⭐⭐
by J. B. Disanayaka
This is an essential book for the beginner. Available at most Colombo bookstores. Although it is a pocket guide intended for tourists, It has one of the clearest explanations of Sinhala grammar
An Introduction to Spoken Sinhala⭐⭐⭐⭐
by Professor W. S. Karunatillaka, Godage International Publishers,
High quality textbook. Good for self study by people with experience learning languages.
Beginning Colloquial Sinhala: an Introductory Sihala Curriculum⭐⭐⭐⭐
Student Edition http://sales.lrc.cornell.edu/products/student-edition-beginning-colloquial-sinhala-an-introductory-sinhala-curriculum
Teacher’s Guide http://sales.lrc.cornell.edu/collections/sinhalese/products/teacher-edition-beginning-colloquial-sinhala-an-introductory-sinhala-curriculum
This is an excellent completely modern textbook but is not suitable for self study. Many of the exercises are only suitable for a group.
Student Reader: Beginning Colloquial Sinhala ⭐⭐⭐⭐⭐
This is a great graduated reader with short articles and matching vocabulary lists.
Readings in Colloquial Sinhala⭐⭐⭐
Readings in Colloquial Sinhala
This is similar to the above book with additional grammar notes.