Why does mathematica take a long time to solve this equation?

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)