  The spin-$1/2$ chain with antiferromagnetic exchange $J_1$ and $J_2 = \alpha
J_1$ between first and second neighbors, respectively, has both gapless and
gapped ($\Delta(\alpha) > 0$) quantum phases at frustration $0 \le \alpha \le
3/4$. The ground state instability of regular ($\delta = 0$) chains to
dimerization ($\delta > 0$) drives a spin-Peierls transition at
$T_{SP}(\alpha)$ that varies with $\alpha$ in these strongly correlated
systems. The thermodynamic limit of correlated states is obtained by exact
treatment of short chains followed by density matrix renormalization
calculations of progressively longer chains. The doubly degenerate ground
states of the gapped regular phase are bond order waves (BOWs) with long-range
bond-bond correlations and electronic dimerization $\delta_e(\alpha)$. The $T$
dependence of $\delta_e(T,\alpha)$ is found using four-spin correlation
functions and contrasted to structural dimerization $\delta(T,\alpha)$ at $T
\le T_{SP}(\alpha)$. The relation between $T_{SP}(\alpha)$ and the $T = 0$ gap
$\Delta(\delta(0),\alpha)$ varies with frustration in both gapless and gapped
phases. The magnetic susceptibility $\chi(T,\alpha)$ at $T > T_{SP}$ can be
used to identify physical realizations of spin-Peierls systems. The $\alpha =
1/2$ chain illustrates the characteristic BOW features of a regular chain with
a large singlet-triplet gap and electronic dimerization.
