What's the adjective for themes? Here's the word you're looking for.
Included below are past participle and present participle forms for the
verbs theme, thematise and thematize which may be used as adjectives within certain contexts.
thematic
Relating to, or having a theme (“subject”) or a topic.
“Instead, Korda squeezes Eisenhower’s extraordinary two-term presidency — not to mention his stints as president of Columbia University and commander of NATO forces — into 140 themeless pages.”