Since NEsper is feature-equivalent to a given Esper version, the download links below point you to the appropriate Esper documentation.
NEsper 8.9.x - Feature-equivalent to Esper 8.9.0
Reference documentation
NEsper .NET and C#-specific information at Appendix - NEsper .NET -Specific Information
PDF print version Online HTML Single page HTML
NEsper 8.5.x - Feature-equivalent to Esper 8.5.0
Reference documentation
NEsper .NET and C#-specific information at Appendix - NEsper .NET -Specific Information
PDF print version Online HTML Single page HTML
NEsper 8.0.0-beta-1 - Feature-equivalent to Esper 8.0.0
Reference documentation
NEsper .NET and C#-specific information at Appendix - NEsper .NET -Specific Information
PDF print version Online HTML Single page HTML
NEsper 6.1.x - Feature-equivalent to Esper 6.1.0
Reference documentation
NEsper .NET and C#-specific information at Appendix - NEsper .NET -Specific Information
PDF print version Online HTML Single page HTML
NEsper 6.0.x - Feature-equivalent to Esper 6.0.1
Reference documentation
NEsper .NET and C#-specific information at Appendix - NEsper .NET -Specific Information
PDF print version Online HTML Single page HTML
NEsper 5.5.x - Feature-equivalent to Esper 5.5.0
Reference documentation
NEsper .NET and C#-specific information at Appendix - NEsper .NET -Specific Information
PDF print version Online HTML Single page HTML
NEsper 5.4.x - Feature-equivalent to Esper 5.4.0
Reference documentation
NEsper .NET and C#-specific information at Appendix - NEsper .NET -Specific Information
PDF print version Online HTML Single page HTML
NEsper 5.3.x - Feature-equivalent to Esper 5.3.0
Reference documentation
PDF print version Online HTML Single page HTML
NEsper 5.2.x - Feature-equivalent to Esper 5.2.0
Reference documentation
PDF print version Online HTML Single page HTML
NEsper 5.1.x - Feature-equivalent to Esper 5.1.0
Reference documentation