To prepare for Lync exams 70-664 and 70-665 use the following materials. Bold links are strongly recommended to view! Don’t forget about Second Shot (until 31 May, 2013) which gives you free retake exam.
Official Lync downloads:
Great book! Helped me a lot to understand Lync architecture and how it works inside. Includes Lync Mobility Services , Exchange and third-party intergrations.
This book doesn’t include Lync Mobility Services. Other subjects (lync enterprise voice and orher) are good covered.