This month, I recommend you read "Design It!" by Michael Keeling.
I re-read this book during April as I felt the need to refresh my basics of producing architecture solutions. Even if you are transitioning from software engineer to technical lead/architect role, this book represents a good starting point for an orientation about what is expected from you.
When in a leadership technical role, decisions based on facts are expected from you. Several years back, when I first read Chapter 6, "Choose an Architecture (Before It Chooses You)," I had my Aha moment: as a developer, I was proud to produce the optimized solution, cleanest code and that was enough to successfully complete a functionality; as an architect, success was measured differently: choosing to produce the best solution under constraints while being opened for future change at scale.
Having a good technical foundation and pattern knowledge helps when managing complexities, yet producing a meaningful architecture is about producing a solution while keeping an eye on its evolving context. In my opinion, architecture is about empowering your team to not only implement it successfully but to gain actionable feedback and contribution to it.
If you are looking for a reading that will immerse you in architectural thinking, I invite you to read "Design It!" by Michael Keeling and leave your opinion about the book in the comments section.