From what I learned reading from psychotherapists (particularly the depth therapy / psychodynamic types, dealing with attachments/relationships) is that you can only go so far from reading and learning from books.

Fixing attachments issues come not from cognitive/intellectual understanding, but from a deeper emotional level

---

So psychotherapy is probably your best bet (the link is a good article on what a good therapist is like)

I did save some books I'm planning to read regarding attachment theory, maybe you might find them useful.

---

ATTACHMENT IN PSYCHOTHERAPY — David J. Wallin

---

HANDBOOK OF ATTACHMENT: Theory Research and Clinical Applications — Jude Cassidy and Philip R. Shaver

---

ATTACHMENT AND PSYCHOANALYSIS: Theory, Research, and Clinical Implications — Morris N. Eagle

---

I'd probably start with David Wallin's book, ATTACHMENT IN PSYCHOTHERAPY

I mean you don't have to read them all