Cover -- Title page -- Part 1 . Problems and main results -- Notation -- 1. Sums of reciprocals -- 2. Multiplicative Diophantine approximation -- Part 2 . Developing techniques and establishing the main results -- 3. Ostrowski expansion -- 4. Estimates for | -- | -- 5. A gaps lemma and its consequences -- 6. Counting solutions to | -- |<\ve -- 7. Establishing the homogeneous results on sums of reciprocals -- 8. Establishing the inhomogeneous results on sums of reciprocals -- 9. Proofs of Theorems 2.2, 2.3 and 2.4 -- 10. Proof of Theorem 2.1 -- Acknowledgments -- Bibliography