It depends on the type of responsibilities within your managerial role. I have found that different companies have different responsibilities for a manager.
For example, will you be performing interviews? If so, make sure you clearly understand the interviewee's POV - take a look at "Programming Interviews Exposed" by Wrox Publishing.
If you are leading the team in a technical advisory capacity, make sure you have strong leadership experience alongside the technical. A good non-technical leadership book is "It's Your Ship" by Captain D. Michael Abrashoff, US Navy.
I was in your shoes before - developer who became a development manager. Some skills I learned the hard way:
- Don't be a buddy, but be a mentor; that's what they need from a manager
- Learn to listen to them; don't make your way the only way
- Challenge their ideas, but not in a belittling way; make them justify their cases
- If people step up to the plate, give them a challenge but enforce that they will be accountable; many people want new responsibilities and to showcase what they can do. Just be sure you pick those who have shown interest and the ability to do so.
- Respect your team. If you respect them, then you are 50% of the way to having their respect.
The other 50% of their respect is to be technical. Some managers become solely managers. In a development shop, you need to know the technical. Maybe not the depth, but the breadth; you need to know what's going on. If you lose the technical, you cannot challenge, you cannot understand, and you aren't up to speed on what is going on in the industry to challenge your team.
One other piece of advice to further you along from what I learned: Make a personal goal to read 2 books for work within a certain time span. Every month I read one book - one business, one technical. This gives me other opportunities to learn new ideas and further myself, but also to apply some of those skills to my team. I recommend reading the occasional business profile - The Google Story, The Pixar Touch - but also books on non-technical companies such as The Toyota Way to learn about lean methodologies. From a technical side, it depends on the work your company does and the technology you use, but books like "Code Complete" can help you spur your team to better themselves and perform better practices.