What you have achieved with this bookChallenges and future directionsSample efficiencyNeed for high-fidelity and fast simulation modelsHigh-dimensional action spacesReward function fidelitySafety, behavior guarantees, and explainabilityReproducibility and sensitivity to hyper-parameter choicesRobustness and adversarial agentsSuggestions for aspiring reinforcement learning expertsGo deeper into the theoryFollow good practitioners and research labsLearn from papers and from their good explanationsStay up to date with trends in other fields of deep learningRead open source repositoriesPractice!Final wordsReferences