You should go through both texts on Hatha Yoga for elaborative knoweldge on Asanas, shatkarmas, pranayamas, mudras and meditations. Hatha Yoga Pradipika written by Swatmarama Yogindra is classical manual on hatha yoga and it has 4 chapters - description of asanas, cleansing practices as well as pranayama, mudras and bandhas and kundalini, and higher stages of yogic practices including samadhi. Whereas Gheranda Samhita is the collection of 7 chapters on cleansing practices in more details, asanas, mudras, pratyahara, pranayama, dhyana samadhi.
But if your interest is limited to asanas and pranayamas, I would suggest you to read one internationally famous and important Asana Pranayama Mudra and Bandha by Satyananda Saraswati. This book is the most systematic yoga manuals available today. This book has illustrated step by step directions for simple asanas and pranayamas to advanced ones, with details of chakra awareness. If you read this self-explanatory and self-speaking book, you don't require to read the above two text books -Gheranda Samhita or Hatha Yoga Pradipika on Hatha Yoga. These two books are meant to be read by scholars or those who prepare for Yoga Certification Exams.
