I want to solve an equation. By Mathematica, it take a long time. What the problem? Can anybody help me?

The code is as follows:

b = FullSimplify[(4 g Sqrt[
 n (1 + n)] (-1 + 2 g Sqrt[\[Eta]]) Sqrt[\[Eta]] (1 + 
   g (1 + 2 Sqrt[n (1 + n)]) (-1 + g Sqrt[\[Eta]]) Sqrt[\[Eta]] + 
   2 n (1 - g Sqrt[\[Eta]] + g^2 \[Eta])) \[Kappa] (\[Kappa] - 
   2 g Sqrt[\[Eta]] \[Kappa]) - (1 - 
   2 g Sqrt[\[Eta]]) (2 Sqrt[n (1 + n)] + 
   g (1 + 2 n + 2 Sqrt[n (1 + n)]) (-1 + 
      g Sqrt[\[Eta]]) Sqrt[\[Eta]]) ((1 - 4 g Sqrt[\[Eta]] + 
      8 g^2 \[Eta]) \[Kappa]^2 + (\[CapitalDelta] + \[CapitalOmega])^2))]

Solve[b == 0, n]